I don't think 40% is too much for a TD, maybe not enough castor. I use Sig 35% in my TD's and have no problems. My medallions respond nicely to it as well. If you are not running the motor for a month or it is stored in a humid envirnment, some after run would help. It also helps to disconnect the fuel lines for storage, this prevents the acids from seeping up into the engine. The older TD's are most likely to stick at the top as they were tapered cylinders. Storing with the piston at a lower point will help too.

I also transfer my fuel into small bottles for use as the fuel tends to absorb water. Keeping the main supply sealed and cool and just taking what I need to the field.