I must admit I can be a bit slack when it comes to quoting for stuff; but if I know I'm going to be late, I always phone the customer and say something along the lines, 'we haven't forgotten about you; we'll be round roughly between(insert days of the week here).
And if we arrange a 'date'; I always make sure I'm there. First impressions count.
But a year later is really taking the mick.
That window cleaner must be on drugs or something.