Highland Neps. 65� - 90�F
Lowland Neps. 60� - 70�F

Source: http://cobraplant.com/index.php?main_page=page&id=32

They can adapt to a wide temperature range, ideally 70-80 but can take cooler or warmer conditions. Not beyond 45 (with some protection) or above 100(with more fans and water-misting).

yeah, my neps routinely experience 90-95 degree temperatures. Just keep your plants misted and insure they have good air circulation.

can they be indoor plants for the winter?

yeah, just make sure they get enough light, humidity, and nutrients; winter can be a rough time for neps, when they are grown incorrectly.

Mine are in a south and west window during mid fall/winter. I do not feed in winter.

I bring mine inside to a south window in winter. Then again, winter can be a tough time for any plant when grown incorrectly.