For less than 5% of the system cost, vacuum valves are a no-brainer in my book. Especially if you travel, and you're not going to get a second chance, even if you can afford the 95% to replace the system immediately.
As for dessicants, I don't understand why that would be desirable. Everything will equalize to ambient conditions within an hour. I dive in relatively (!) high humidity locations but also relatively high temperatures. Those two factors tend to go together. I have yet to see any problem with condensation inside the housing.