Vermicomposting

With temperatures taking the deep dive (zone 5b) I moved my worms indoors. That Storage tote got really heavy so I have switched over to the bucket system for the winter.

As I see benefits to this 5 gallon system I also see a pretty big con.. size of the bucket and how large the colony can be. I reading numbers ranging from 500 to 1500.. I have 3 buckets setup now with all of 500 worms (of ranging maturity) in each. Seems I'll be filled up fairly quickly..

What are the thoughts of colony size?

I've read 800 to a thousand in a 5 gallon bucket. So I think you should be fine.  I think I read they will self regulate. If it's to cold, or hot or there's not enough food, or space then reproduction slows down.  I think the key will be to keep an eye on them, and see how it goes.
Wish I could be more helpful. I live in zone 9b, so my worms are fine outside year round.  Lots of people keep there worms inside, and lots use 5 gallon buckets, so it seems like you will be good.  
I did read you should have a minimum of 50 worm, so if you decide to divide them up you may want to make sure you have at least that many.
Wish I could be more helpful. Good luck