My black one has had a good coat or 2 of wax already but I still need to wash it every week to keep it looking nice and alloys clean!
One word of warning though - I had a scratch or 2 to get out the other day and the polish has left holographic marks to an extent I haven't seen before!! Going to get some Auto Glym to sort it out this week but worth being careful with it!!
I wouldnt bother with Autoglym. It aint as great as everyone makes out.
Save some money and go to halfords for some MEGUIARS car polish. They do something called "scratch-X" which very effectively removes surface crazing and light scratches whilst not damaging the paint work.
Another trick to avoid swirling is to put the wax on in a straight line by hand (you can do this better with a hard wax like Zymol).