How long can I watch tv while wearing my glasses?

No limit. Glasses improve the clarity of the view and can be used for this purpose on viewing tv. The only damage you do is that the content on tv is sometimes questionable.
No limit. Wearing glasses has no effect or limit on watching tv. You can watch as little or as much tv as you want whether or not you wear glasses. You might have less headaches & eye strain when wearing glasses depending on your reason for needing glasses.