I havn't had mine very long, and asked a similar question right after my aquisition. After about 8 months, here's my observation.
It's nearly as good as it gets the way it is. Make sure you get these few items:
Sling
Replacement grip
Not less than 10 milspec mags
More ammo than you can comfortably lift all at once.
Now, here's what you do:
Shoot. A LOT. Learn to use the irons before you put on ANY other optic. You might find, as I did, that I can do better with iron sights in most situations, than I can with any other sight, and I don't have to worry at all about cost or fragility.
That's it for me, anyway.....