When are titanium valves needed

When would you suggest using Titanium Valves?
Is there an RPM limit?
I typically shift at 6800 and rarely take my engine to 7400.

For your average drag raced big block build with an .800" roller cam I would think that 7,500 rpm is a conservative limit knowing that others may go to 8,000.
Valve train stability from shaft rockers, pushrod flexing, titanium retainers will move the limits. If you are using stud rockers I suggest going to shaft rockers before changing the valves.
Also most important will be changing the intakes to titanium over the exhaust. Weight reduction is around 30%. Some say 25hp gains at 7,500 rpm for the intake valve change alone.

FYI- I have no personal experience with titanium valves. I will always stay below the titanium rpm requirements while trying to understand the limitations with stainless valves.

I use the 7 number . .700 lift and 7,000 rpm on a valve over 2.050 in diameter OR over 100 grams in weight. Not AS important on flat tappet cams as they are with rollers. I've been using titanium valves since '75 , and they are grerat but not "bullet proof". I run Stainless on street stuff and stock valves when it doesn't matter. A 4,000 rpm pickup truck doesn't need a back cut pro flow valve.