Hey,
Here it is my suggestion:
STR should be increase as percentage of current STR. For instance, If I have 100.000 STR, I will increase my str only 10 point every day. However, If I have 10.000 STR, I will be able to increase my STR 100 point every day. It will be inverse proportion. Numbers are just example.
Level also can be included to formula. 20 level guy with 10.000 STR can increase STR faster than 40 level guy with 10.000 STR.
This will make everyone happy.
