This generally depends on uninstall portion of the software, you're uninstalling. Like - how well it cleans up.
There will probably be some log files left, some registry keys.
On evaluation software - it will record, various statistics. Like how long you've been using it and if you haven't gone past permitted evaluation period.
If you have system restore enabled, then sysrestore used space will increase after uninstall.
So some manual cleanup may be necessary.
But if you're not constrained by available space and uninstal process has no bugs in it and you're not trying to circumvent some evaluation restrictions, then there should be no limits on number of possible installs/uninstalls.