Well I think the .tmp files are just building up - and the renamed. So they are not causing any actual excessive write.
As for the gmap - it would be cool if there is a mode to not write them.
Actually it would be great if mkgmap could write all in one go. Because the thing that takes so much time - is the address search - and that is always the same. The differences are tiny (just because MapInstall is crashing when files are missing) you need to compile them separately.
but maybe there could be a mode where mkgamp writes all in one go.
So family-name / family-name1 / family-name2
description / description1 / description2
input input1 input2
family-name..
show-profiles
overview-mapname
product-id
(and maybe I missed some options are those that would need to be given for each set of input tiles. And then just an option where you tell mkgmap files starting with which first 4 numbers are relevant for address search. No need to analyze if those other supplied .img (e.g. buildings or contourlines) need to be added to address search.). I know coded around the problem of the gmap files causing excessive writes. But yeah that is actually really complicated be it on windows or linux...