SAP doesn't restrict the multiple assignment of a role to a user.
This is also useful if you want to assign roles for different durations
EG:
X:P7_9053_VA01 01.04.2013 to 31.12.2013
X:P7_9053_VA01 01.02.2014 to 31.12.9999
prgn_compress_times will remove the duplicate entries.
Eg:
X:P7_9053_VA01 01.04.2013 to 31.12.2013
X:P7_9053_VA01 01.05.2013 to 31.12.2013
X:P7_9053_VA01 01.01.2014 to 31.12.9999
prgn_compress_times will make it as a single entry:
X:P7_9053_VA01 01.04.2013 to 31.12.9999
Regarding the profile overflow issue, there will be only 1 profile assigned to a user for a role.
Regards,
Dinesh