I have been making my own MM fondant as I like the flavour (and the money saving) much better. The recipe I use contains only marshmallow, water and icing sugar. My question is 3 part.
1. How long will it keep?
2. Will it work for modelling if I add Tylose powder to it?
3. Does it require refridgeration.
MMF keeps for months. I don't recommend using it to cover a cake after a couple of weeks, but for figures with a bit of tylose, it's just fine. I found that figures will set up fine, and last for ages. I did have a problem when some figures were kept in the fridge, they started to "melt" all over the place. Add your figures to the cake at the end, and they'll be beautiful.
Ditto, I love to work in MMF. I have made flowers and mold figures with MMF. I typically keep it wrapped in plastic outside the refrigerator until I'm ready to use it. It keeps for months. Best wishes in using MMF in your next project.
I love MMF too. I often make figures out of it, sometimes I've tried adding tylose powder and didn't like the consistency as much. I've also tried sugar paste for the figures but it dries way too fast. MMF is definitely my fave.
As for storage of unused MMF, I've kept mine in the cupboard, wrapped in saran and then sealed in a ziploc and it keeps reasonably well. If it feels to hard to work with, try putting it in the microwave to warm it a bit. I agree though, I wouldn't cover a cake with fondant more than a few days old as the consistency is different. I find old(especially colored) MMF is a bit drier even though well wrapped.
To store the figures, flowers, etc., I let them dry and then put them in a non-air tight container in the cupboard. If there is too much humidity or sometimes if they are sealed too well, I find they soften back up, not ideal for something you've worked so hard on. They seem to keep indefinitely if you can keep them dry.