Brandon,
That is dependent on the rpm, boost and how aggressive your cam is. If you have a cam with over .280" lift which would equate to around .475" which would be around 1.465" spring height, you need better springs. At that point the 60lb springs have the exact same spring pressure as the factory springs. I would say 60lbers over 3500 with a performance cam or stockers over 3500rpm with a factory cam or over 45lbs of boost need better springs. Also if you have bigger than factory valves you don't have enough spring pressure.
Let me know if you need any more info.
Zach Hamilton