For me, it depends how good the first experiece of using it was. If it was amazing then I review it asap, if it's not so good or I'm unsure, I'll try it again a couple of times to get then full feel of it before it write a review. I like to be honest in my reviews and feel that some people only write good reviews for the sake of it and to impress LH.
I don't think very many people write good reviews to impress LH - I think some people are just really easily impressed with toys and everyone is different - things that I find amazing, you might hate and vice versa for example.
Many of the tester people get picked because they give well balanced reviews and many people outside of the forums don't really know you can get sent testers so have no reason to "impress".
Oh and to answer the Q - I like to use something at least a few times (even if it's amazing) just to make sure I'm absolutely sure of my verdict before reviewing because it's easy to be influenced by other factors.
With testers I will try it out a minimum of 3 times before reviewing (more if I can't decide on the product) and with things I've bought it can be from 3 times to 100 times since there's no time constraint and it depends when I get round to it/how long it takes me to decide on how much I like the product.