Tee selection at St Andrews

We normally play in the winter and on a Sunday, (so no chance of the Old Course) and winter tees are in place. Quite often though we see players teeing off from the back tees including the first tees next to the starter's box, so as long as you're not causing any delays I don't suppose anyone would object. However some of the Championship tees for the Old Course are beyond what is the normal boundary of the course. (I think the 12th is on the 3rd fairway of The Eden)