Some of the teks recommend going easy of the evaporation of salting water, when using vinegar it is indeed wise to take it easy once its reduced down, but when using fumaric acid in your salting water you can go mad pretty much.
I got a bit careless, left my FASW boiling away and ended up boiling my DMT fumarate, i have no idea how long it was boiling away, but it was bubbling like mad when i got back to it.
Once left to cool down it formed a firm crust of crystals.
I cleaned this up (removed the excess acid), freebased and pulled with acetone, ended up with perfectly good freebase.
The only thing that you should worry about is going from boiling water to boiling dmt and not realising, waiting for that last bit of water to go while losing DMT to the air.
It might be possible to burn the DMT fumarate if using a gas burner, but on an electric hob you're pretty safe.
Anyway this is a long winded way of saying, don't stick your water in the oven and wait an age for it to evaporate, it will be hard to ruin DMT fumarate.