The toilet must sit firmly in place. If the toilet moves a little when it is sat upon... then it only takes a few days or a couple weeks for the wax seal to loose its seal. The way to test it is to sit on the toilet and get up... while a friend carefully watches the toilet and also watch the drain pipe under the floor to see if any movement occurs... such as the floor joist bending or flexing just a little. (Use a flashlight in basement to look at the pipe movement.) If movement of the toilet or pipes or the wood floor is seen when the friend gets up or sits on the toilet.... then that is the problem. Floor joists might need re-inforcing (add more boards or support brackets to stop the movement. Re-inforce and replace the wax ring again.
Another problem is some floors have a floor drain. If the water is evaporated out of the P-trap in the floor drain... then sewer gases can come up. Just pour some water into the floor drain every few weeks to keep the floor trap full of water.