Yes, I have previously been to a Christmas in July, and it was great fun.
I have not been to one in about 4 years however -have not been invited and don't know anyone who has them apart from restaurants.
Do you know what, I have been invited to such events but I don't attend.
I think that what makes Christmas special is that it comes once a year and to be honest re-scheduling it so we can more of the same, more often, takes the shine off of it for me.
I am all for getting together with your friends and family and celebrating their importance in their life. Perhaps rather than using Christmas in July as a reason we could simply get together anyway without the label of Christmas and keep it exclusively to the 25th December??