Is it safe to Overclock/run my GPU Like this? 5850

[sitefive]

Totally new to this mining/overclocking,
got a 5850 card yesterday with default settings it gets 305kh/s
however today I overclocked it from Stock 725/1000 ( GPU/memory clock)  to 925/1050 and in result Im now getting 385kh/s which is about 26% increase which is Nice! Temperature is constant at 76-77c (have taken off the side panels for more airflow as well)

Can anyone tell me is it ok to overclock it like this and run it at those temperatures?

[sitefive]

also whats the max safe temperature to run such temperature for extended periods of time? I now run it at 80c just because its so damn loud if I set the fans even a bit higher and I have to live in the same room as well!

[Prolifik]

You want to keep it under 80C ideally under 70C
Overclocking can't do damage unless you're adding voltage or letting the card overheat.