I am a big believer that you should try to work avocado and other healthy vegetable oils into your diet as much is possible, even every day. The health benefits of these unsaturated fats are undeniable and avocado also contains many nutrients that are vastly beneficial to your health.
The most important thing is to properly balance the portion size to fit your dietary needs. Remember that avocados and other foods high in fat also contain quite a bit of calories. It is easy to take in more energy than we intended to when we eat dense foods such as these.
Exactly how much avocado is right for you is ultimately a decision that you have to make for yourself, but I can give you a few guidelines. Many men with moderate exercise activity can get away with eating a whole avocado every day. Most women would probably find it more appropriate to eat a half of a medium-size fruit. I recommend storing the other half in an avocado saver in order to keep it fresh and green longer.
Other than the caloric intake, there really is no other negative to eating a lot of avocado. It is wonderfully healthy for you and dense with nutrition. There are certainly much worse vices that you could succumb to. I often buy a package of half a dozen and eat one per day as they ripen on my countertop.
So try to tailor your avocado intake around these guidelines, and come up with a plan that is sensible for you. Nearly everyone can eat at least a few small slices of avocado every day and reap the health benefits from it, without gaining the extra girth around their midsection.