When is it necessary to move to one piece valves?

I've read various reports of OE valves being fine for mad power, but understanding the danger of valve seperation (and the obvious massive damage this causes) I'd like opinions on when it's best to use them...

My current situation is I've had my valve seats re-cut and I've lapped the valves in then proceeded to shim the heads up. Needless to say I'd rather not change valves at this point as I'll have to do it all again , however if it's prudent then I'll do it..

 

bttt

 

bttt

 

With any engine build its only as strong as its weakest point, if you thinking of doing the valves I would do them for peace of mind as it is one less thing to worry about.

Banny