Hi funzero,
STA tools are used for Timing sign off. By simulation tools , you cant say design can run at XXX frequency.
Lets how STA tools will work.
STA tools will divide the logic of the design into Timing Start points(SP) and Timing end points (EP). Valid SPs are Input port /FF clock pin and valid End points are FF Data pin and Output ports. After applying the clocks and your constraints, STA tools will try to check the timing path (Path is from Valid SP to Valid EP). Assume your design is single clock and it runs at 111Mhz(9ns). Tool will try to check every path will work at 111mhz or not. It wont check beyond that(Becasuee you constraint say check only for 111Mhz). Even though one path works at 150Mhz, it doesnt mean, your design can run at 150mhz.
Hope you got it..
Regards,
Sam