How many skid spots is too few?

I made a bit of an error - got new cranks last week and got a 45th chainring instead of the 46th chainring, as that was all they had.
I checked that the gear inches would be ok as being a real geek, I had a chart in my bag so I could work it out.
The problem is that I didn't check how many skid spots I would get. And its only 2.
How much of a problem is this? If I change the rear cog it'll make the gearing too hard, so I'd need a new chainring and a new cog to sort this out

rotate the wheel a few teeth further on every week.

why can't you buy a new cog? i don't quite get it.

as far as I know you can just shift the back wheel once the marks that you have become substantial

edit: got beaten by pj

I'M USING 46: 18 at the moment. My gearing is pretty light - 67.5 gear inches, and that's the way I want to keep it
If I put a 17th cog on (the next one down in size) then I'll have 71.5 which is much higher than I want.
I could put a 44th ring on and get 66 inches, or I'd have to use a 46 and a 19 to get 66 gear inches

don't worry too much about the skid spots, it rarely matters much unless you like to do 30 yard skids outside the pub like Hillbilly.

just move the wheel round a bit when you start seeing some wear on the tyre

put the 17t on and stop moaning. you won't even notice it.

unless you've got/had polio, in which case stick with the 67.5.

oh good. Thanks everyone

according to rabbit, 45/17 is 69.6 with 17 skid patches..(with 700c x23 tyres)

so see how you get on, you can always pick up a 17t cog later