fit-PC3 developers:

If you can, add the heat sink case as an option for the low power units that
normally have simple cases. Some of us use the devices 24x7, 365, for
years. My old fit-PC 1 has been powered on for 2.5 years. I'd like it's
replacement to last just as long or longer.

Or you can sell the empty heat sink case separatly.

(The only reason to upgrade for me is that I am starting to use my fit-PC 1
as a media server. Need more space but prefer internal. Though I am
considering replacing the PATA 2.5" drive with a larger one.)

I'm glad to hear fit-PC1 works well for you.
The standard case of fit-PC3 is thermally sufficient for the thermal needs of fit-PC3 LP, Basic and Value in in-door environment.
We may be offering in the future the LP version in the ribbed case for extreme environments.