Neil R

If everything else is spot on. Training , diet, rest etc then 2-4iu a day for 6 months should give you noticable gains that should be permanent. You can't really put a number to it as everyone is different and generally the older you are the better the response.
If you can aford it and want to try then by all means do so. You should be pleased with the results.
A lot of people would prefer to use the money to buy more gear in, but its each to his own.