The TLD does not give a website any advantage in search. Some people will tell you that .gov and .edu get special treatment but it is not true. There are no arbitrary bonuses in search. A crappy .edu will rank the same as a crappy.com. (In fact most .edu pages are not even published by universities).
If you have been using a particular domain for five years I definitely would not change it unless you were able to a new domain with better keywords in it. Even then they would have be almost exact matches for the most popular terms you are trying to rank well for to be worth making the change.
If you change domains you have to make sure you do 301 redirects from the old URLs to the new URLs and that will cost you some PageRank. Additionally, there will be a transitional period where your rankings will drop or disappear as Google completes the process of indexing the new URLs and processing the 301 redirects.