I currently have my guitar hooked up to an rp250 effects pedal by a nice 12' cable and the pedal attached to the amp by a Monster brand 20' cable. Is there too much cable there and would I benefit from purchasing a shorter cable?

Thanks in advance,
the shorter the cable is, the better the sound quality. but I don't know if you can really hear any difference
A hero of war, Yeah that's what I'll be

I have the same exact set up. i dont think it makes any difference really, and plus youd rather have too much than too little.
With guitar cables, the sound only starts to degrade around 25-30 ft, whereas with XLR you can have up to 300 ft before sound quality starts to degrade, I'd recommend trying Mogami, they're good for studiowork, they're Quad Shielded and are pretty much as clear as can be( clear being the altering of your tone).
Quotation is a serviceable substitute for wit- Oscar Wilde
It all depends on the type of signal. An Instrument signal from a passive guitar pickup is a high impedance signal and will begin to degrade quickly. If there is a signal buffer relatively close to the guitar in the signal path, then you can easily have a couple hundred feet of cable as it will reduce the signal impedance.
ESP LTD EC-256 and a Fender Deluxe VM
Thanks for the responses you guys are so fast and helpful!

The guitar I am using is epiphone les paul standard with stock pickups --> 12'cable ---> RP250 multi-effects processing pedal -----> 20'cable ----> Line 6 Spider II 30 Watt amp.

As I take it you are saying that I will likely have very little difference if I swapped out one of the cables for a 3' or so? Most my work is done in close proximity to my computer, no stage work for me.

* The cables are both decent quality, a monster one, and a very thick shielded fender one.