If you love her and she loves to see/feel you come or have penetrative sex with you, then I see no way how you could deny her that pleasure.
Take what you get, and be happy with it. There may come a time where she suggests a longer play-period on her own. Don't press her into it. It may backfire.
Currently using: Gerecke Desire (Titanium)
Owns: CB6000, Bon4, Sentinel (Copy), Birdcage (Copy), Lovejail