I have about eight or so 1gb cards in my bag kinda collected them over time
I'm happy with swaping cards if I'm having a long day after it only takes a few seconds anyway.
Using a bigger card size may become more of an issue if you continuely shoot RAW images as a 1gb card is just not good enough for the job.
I've found that I can get 1gb cards for as little as £17.99 for a 133x their own brand but I have one and it works fine for me. Site URL below.
http://www.mymemory.co.uk/
When 2gb cards get down to around this sort of price I think I might change but until then I'll use 1gb cards.