GF1 Video Question
Good chance your 4Gb SD-cards are not class 10 but class 6 (at least all 3 mine are). However, that's good enough for any format.
When you shoot Motion JPG in WVGA or VGA (in stead of in HD) you can record 21 mins 20 sec of video on a 4 Gb SD-card. Maybe you can first try out the difference between HD and VGA or WVGA and see what is acceptable to you or your wife.
I use this WVGA format a lot when taking videos for a group of musical friends who are totally happy with the results. Personally I'd prefer HD, but oh well, I'm not prepared to buy them a 16 Gb card, and most certainly not after learning about Dan's adventures with his 16 Gb cards.