Correct. In the summer flying rush I only flew -700s for 3 months straight, but then in September I have 4 -200 trips and one -700 trip.

Different bases have different airframe mixes. IAH only has -700s, as pointed out, while PHX (I think) only has -200s at the moment. MSP has a mix, but you'd have to bid above 20% to reliably be able to get anything other than a -200.

Good story...while on RSV, having completed -900 OOE and having only had 4 landings in that airplane, I was assigned a -900 trip with a RSV captain. Halfway through the first leg the CA turns to me and says 'Hey I haven't landed one of these things in about 4 years, do you remember the technique?'

Then his PFD and MFD went blank on downwind, so I had to land it, despite not having landed a -900 in about four or five months. It was fine, though. (For those uninitiated in the CRJ, the -200 and -700 land extremely differently, requiring different techniques in throttle reduction and flare. If you forget what variant you're flying and mix up the techniques, life gets a bit more exciting 30 feet above the ground. The -900 is rather similar to the -700, though...you just have to flare it a bit more.)