For me the three and a half days is a pain, I think it should come down to 2 days (even 3 would be better than the added half)
I am sure if the price were reduced to £2.50, £2.00 would be better, and allow you to try every 2 days, SW would actually make more money in the long run. Supermarket tactics, reduce the price and bring the people in
(they always buy more than they went in for)
Regarding the checker it is such a useful tool, as you say it is cheaper than a visit. Only prob. is there isn't any feed back like you have from a visit. For instance if you go and your word gets phoned through you know some letters are right. Not to much help but a little.
Lets vote for £2.00 or £2.50 and every other day
Perhaps shouldn't have given the £2.50 option