The two of you need to practice the exercise I recommend for this very purpose whether in response to Premature Ejaculation, or as in your case, just wanting to hang in there a bit longer.
Please do an advanced search using my name and the key words: Benchmark or sense of urgency and read about it. Here is one such post:
http://www.sexinfo101.com/forum/new_...ight=benchmark
You can also do the squeeze technique. Google it and read about how it can be helpful.