You sound a bit bored with your routine. Break it up by doing Chess Mentor, going old fashioned and using a book or playing against the computer.
Tactics plateau

10-15 minutes is a good limit IMO.
60-100 puzzles in a 1 day is an awful lot. Any puzzle you can solve in less than a minute is trivially easy. Probably a good difficulty is around 3-5 minutes (I don't think 10 minutes is bad, but like you said you don't have time for many of them). So anyway at avg 4 minutes a puzzle you're looking at 4 to almost 7 hours of tactics to solve 60-100. Besides not being too useful it will probably also burn you out.
For puzzles that you got wrong review the solution and all that. And if you think it's a worthwhile pattern / common blindness then I'd save the puzzle (bookmark it on your browser, write it down, whatever) and wait a few days or until you have a small collection of them and try to solve them again.
Plateaus are normal. Maybe tactics is your strong point now. Maybe you're getting burnt out. Either way sounds like it'd be good to switch up the training.

I find that tactics exercises expose the fluctuating reliability of my ability to calculate. Some days are better than others. Sometimes I remember problems I have seen before and solve them correctly right away, and other times I don't recognize them until after I have blundered. Sometimes I fail most of the problems I see for a long stretch, and then I solve a dozen or more in a row.
One of the patterns I've noticed is that about an hour into a tactics session, my eyes will seem to glaze over as I enter a "failure zone". I will think less and click more. I don't drool or anything: I think I just reach a state of calculational tiredness that prevents me from tackling the problems as I normally would, and my rating can drop like a rock. The fact that I keep after it in this state is a testimony to how addictive tactics problems can be.
As this point, I try to limit my sessions to about 45 minutes. I also delete my progress each time now. I found myself getting frustrated with the way the RD element of the rating equation affected my results after solving thousands of problems. This separates me from the ego-altering influence of the rating to a degree, and it's easier to avoid that failure zone.

Coach Heisman's take on reaching plateaus in tactics training is that you haven't spent enough time on the most basic problems. Of course I'm paraphrasing here (and probably doing a lousy job to boot), but Coach likes to use the analogy of the multiplication tables. Sure, you can kind of skip over them and go on to higher math but it's awful inconvenient to have to add up 6+6 seven times when knowing 6 x 7=42 is much easier. At a certain point you do have to understand multiplication or you just can't go on. Coach is a big fan of Soviet style "learn the basics "till your eyes bleed" training (OK, that's my phrase, not his). Chech out danheisman.com for more.
I think I've found an easier way get Soviet style training than digging it out of books. WGM (and 12th women's world champ) Kosteniuk's husband is a programmer and he's come up with the best computer software I've yet found for no nonsense training-ChessKing. The main program is just so much easier to figure out than Fritz and has a wealth of training options as well as 2 giant databases and a strong engine (Houdini 2). It's almost idiotproof and even a neoLuddite computer user/abuser like myself is able to use its' features. There are also 6 standalone programs to drill you on 3 levels of tactics, opening theory (imagine an animated FCO), endgames, and strategy. You can get the whole package for around $140 either direct from the ChessKing website, USCF sales, or Amazon. It's reinvigorated my training and I don't think I'll need anything else until I bust 2000; yes it has made me that confident, and I'm just an old patzer (probably with delusions of grandeur, but we can all dream, can't we?)
Sorry everyone for the late reply. A combination of being busy and lazy. :P
texasyankee, I plan switching it up a bit in a couple of weeks when I get the time. Probably start playing more games than I do at the moment.
waffllemaster, you make some good points. On second thought I only remember doing too many puzzles at the beginning when I both had lots of hours to burn and the puzzles were probably easy. I may have been a bit hard on myself expecting the slow improvement to be faster.
Fingerfly, you hit the nail on the head! I think you described what everyone experiences. To me it's even more frustrating when I'm aware I've entered the failure zone and can't help it but I am in the mood for some puzzles. These days I also tend to keep my sessions short and may even cut them shorter if I'm not being productive. But with multiple sessions per day they add up. :)
baddongo, this is unfortunately a piece of software I can't afford at the moment. You described though something that I was worried about. That maybe the reason I can't improve is because my pattern recognition doesn't match the difficulty of problems I'm attempting. Practice does require a lot of repetition but I was afraid that I was approaching the puzzles too superficially to learn anything from.
A few months back my rating was hovering at average low levels and after having done a lot of puzzles at chess tempo it skyrocketed both here and there. I don't care about the rating and it's circumstantial at times, but it can be a relative measure of improvement.
For over a month though I've reached a plateau and at the same time I don't like how you have all the time in the world at chess tempo to find a solution. So I give myself 10 minutes tops for the harder ones. But even so, at times I lose my concentration or patience and can't even analyse.I've also suffered a dip here because I don't seem to care. I am too slow. I can spend about 2-3 hours on chess daily and ideally I'd like to be able to do 60-100 puzzles but sometimes I don't even get past 30.
What should I do for the puzzles I get wrong? Accept missing the shot and move on, or keep analysing until I solve it? I feel your perspective of the board changes once you commit to a move and then realise it's wrong.
At the moment I'm mostly doing tactics at home and I play weekly at my local club (not always for serious). Am I need of some holidays or do I need to change my approach?