Phil
For the last 2 years you have not increased your prices, yet everything that you need to live and survive on has gone up, some of these prices are really quite small but others like car fuel, gas, electric and morgages have risen by more than 10 times the rate of inflation.
If you train your customers that every year or 2 you will increase your price to reflect the ecomony, they won't moan too much.
Times are going to be harder for some in the next few years, because of this credit crunch we are going though, but remember you have to look at your familys' interests first, and not increasing your prices will affect them.
If you have 150 customers and you charged them £10.00 per month for their windows to be cleaned, if you increased your prices by £1.00 a month, you might get 5 who might cancel, but 145 will pay the £1.00, so now you are making £145.00 per month for less work.
If you want to help those customers who simple cannot afford you, them change their cleaning rota to 6 weekly or 8 weekly, but you need to raise their total cost up by 50%, doing it this way, reduces your customers bill by 50%, but increases you take home pay by 50%.