Your figure of a 170 sounds right to me; you could possibly increase that up to 15% or reduce that figure to as little as 50.
Having to few customers creates its own issues, same as I think going over the 200 mark that has its own different issues. An individual can only do so much although there will always be exception to the rule. If everybody starts saying they have hundreds & hundreds of customer, this starts alarm bells ringing and I cant help but think something is wrong else where. Customer number may be very good, but are the hours & prices?
All aspects of your business will be interlinked but some confuse more customer numbers with money. Time, prices, customers are all separated trick is to get the best blend for you.
But I live on an island and theres only 172 houses, I do all of them except mine and a dirty tramps down the road. I pay the tramp additionally to clean my windows, he does them fortnightly, but my round is only done every 3 months. I pay him way too much over the odds but havent got the gumption to put my own prices up. Im sure the tramp earns more than me; he does by the hour thats a fact.
Actually, my example might appear to be joking but it illustrates how your figures are unreliable; simply becasue you dont know my personal circumstances nor my work wishes/targets/limitations bla bla bla
I already said there are varying criteria which affect how many houses a window cleaning business runs. There are other criteria too, value of each property, what if your average price was £45.00.
Your figures are more suited to a one-man-band setup, but try applying them to a crew of 3 guys. Or a couple of scally-wags dodging the tax.
It NEVER is as black and white as you make it out Ewan; which is why I said you cant work to a formula.
It strikes me that the figure of 200 to aim for and then try to slim down is possibly appropriate to your circumstances but it isnt necessarily the case for everyone. Some may need 300 to aim for whilst others settle for 120.