In my option your only line of defense is a sealant. I highly recommend them to help with bird droppings, acid rain, hard water, and complete UV protection. It will also help with getting bigs off, for they will not stick on a seal like they will on bare paint.
Even the best/most expensive wax's in the world will only give you a month of protection. Some idiots think that Zymol Vintage will give you as much protection as a sealant, but they are smoking crack and are highly mis-informed. So wax is only going to give you minim protection for a minim time, as for sealant will give you maximum protection for a longer period of time.
Wax is used for beauty, and sealant is used for protection.
For my personal car, and my clients that are looking for the toughest protection, amazing beauty, and a new car look; I do the following steps to ensure quality and strength. This is needed 1-2 times yearly for protection depending on climate characteristics. But minus the polish for you should not need and do not want to correct a paints finish more than once a year to ensure you have a good amount of clear left to protect the paint.
4. Seal (I use JetSeal and let it cure on the paint for 12-24hours)
5. Wax (Concourse grade and up)
6. Finish with a quality QD to give that last bit of shine and to ensure the paint is completely prepped and protected.
If you have any more questions, please feel free to shoot away!
2006 E90 SG-Dinan Ram Air Intake-Dinan Throttle Body-Dinan Exhaust-19' Hyperblack CSL's-15/5 tint-Matte Black Grills-M3 Spoiler Lip-Amber Delete-Smoke Side Signals