To be honest, I don't focus specifically on any convention. The thing with BabsCon is that they had a TON of guests and those guests needed a ton of art all at the same time!
I mainly just draw whatever the VAs and staff need. Naturally, the time when they need the most stuff is during convention season and especially if one big convention with several VIPs is taking place.
The exception is GalaCon who have been incredibly nice to me over the years. I try and make sure they get as much special art, themed for their convention, as possible.