It heats for about 10 minutes then just stops heating. Compressor keeps running but no heat. I've been told too much freon will cause this. Is this true?

If the compressor keeps running but no heat is being supplied many different parts can cause the problem or similar problems. My suggestion is that you contact someone who has the correct tools and knowledge to find the exact problem.

Working on a heat pump system takes special tools as mentioned above but also takes a high level of skill and knowledge of heat pump systems so it would be best for you to conatct a local HVAC company to do a on site inspection of your system to come to a proper conclusion and make the repair.

It was too much freon.Last spring I had my compressor serviced.They checked the freon and claimed it was low.checked for a leak then added freon.

Yep that happened when the charge is not weighed in or the super heat or subcooling test is not performed. All last summer your electric bills were higher also because of the over charge of refrigerant. Great service company. LOL