Personally I never give a telephone 'Guesstimate'
I've found that Customers will generally describe the carpets as 'not too bad', 'just the odd mark', 'It's not a big area', I don't want to spend too much' etc. etc. :
They generally fail to say 'It's Trashed', 'I live on the Sixth floor', ' you can only do it on Sunday's' , oh , and you can't park within half a mile' !!
I do ask if they're working to a specific date, (if they are it's normally 'Tomorrow') in case I'm already booked up.
But overall I find an on site visit is worth a hundred questions.
Les