The other potential gotcha is that you may be given the higher level quite early on in the SID. In the meantime the controller may have to deal with non-expected conflicting traffic (say someone on a requested heading to avoid w/x for instance) and the only thing that saves a woopsy is him remembering that he gave you a higher level some time ago.
This strikes me as very very dodgy with no obvious potential gain. Far too much projecting ahead required on the part of the controller, who cannot just clear & forget for the reason I envisaged above and no doubt many others.
Truly, if it ain't broke don't fix it.