This may be the first time I have seen ALL useful information about the subject by previous posters - APPLAUDS AT HIS COMPUTER!
Building routines allows you to chunk information - this is what comedians do for long sets. It helps, but tihs is more of the latter stages of learning, but you can still use it.
Writing them down does help - as it allows you to keep organized - write your sets/routines down also.
HOWEVER - FOOL nailed it on the head - the concept of learning includes retention - if you got your dog to plat dead - just because he did it once, doesn't mean you taught him...consistent response to the stimuli shows learning.
You are "seeing" and "trying" new effects, but you move on so quick you aren't actually learning. This is too bad, as you are just wasting your time spinning in circles. You will do everything poorly, rather than a few things well. Having a critical eye of what will work and won't will come with experience - in the meantime, take time with what you learn. Nothing is a waste - I have taught many magicians, and said - what you do now...you won't do it later, but you should still do what you do now well - as they are building blocks for your future.
Like in sports, master the basics, and things won't be so hard to remember....as you won't have to think about the moves and the sequence...just the order in which you need to apply them...which will allow you to move quicker to building it into a presentable effect.
SO - to answer your question - what do I do with my older effects? It depends - does the newly "played with" version offer any advantages, is it stronger or have a more direct approach? If so - I may replace it - I may do both - or I might play with the new one for awhile...then toss it with the many other effects I have tossed aside.
Not all magic out there is good magic - look at things more critically - you will see not everything is worth learning - hell, if we tried to learn everything we saw or read...we would never get anything done in the way of SHOWING magic.
I feel this post was cluttered, but with the guys above - you have a clear direction.