Things at Comair are still in a huge state of flux because of the strike and growth. It's all good, but it's awful tough to give you any averages. I finished IOE on Thanksgiving Day. I was about 30 numbers short of a line for March. I have a realistic shot at a line in April and a real good shot for May. That would make it about 5 months or so on reserve.
While on reserve you get a 75 hour minimum guarantee, so unless you are trying to build flight time money isn't an issue. You are going to get paid at least the 75 no matter what.
There are a lot of newhires currently in training and IOE so flying while on reserve is scarce unless you are trying to make the FAA mandated 100 hours in 120 days. In that the case you go to the head of the line until you get your 100. After that it slows down real quick. We also have a choice to 'bid to fly'. What that does is reverse the seniority while on reserve. Instead of calling the junior guy out for a trip they pick the most senior guy that has bid to fly. Of course they still pick the guys needing their initial 100 hours first. I've been bidding to fly and I'm averaging about 35 hours flight time a month.
It's nearly impossible for a reserve pilot to pick up open time. You can only accept open time that won't affect your reserve availability. That means you basically can only take open time on your 'hard' days off and you still can't exceed the 30 in 7 rule, no more than 6 duty days in a row, etc, etc. It's very impractical to get all the planets lined up to take advantage of open time while on reserve.
I hope this helps.