When are you changing your string and who do you have do it?

I have a two year old BowTech Guardian and am thinking of replacing the original factory string. Not sure of the shot count.

Any reason to use a BowTech dealer as opposed to another dealer? BowTech string or specialty maker?

I shoot a BowTech Tribute and ordered replacement strings from Winners Choice thru Sportsmans Warehouse because I was lazy and they were convenient. I'm pretty sure you can order online from most of the major stringmakers.
I swapped the strings 6 months after I set up the bow and was sure the factory strings weren't streching or changing.Rolled the factory strings in a ziplock and they travel as emergency backup along with the peep and stringloop.The new strings are 3 years old and showing no stress.
I change them myself with a Bowmaster(cable) press.
I would like to believe most aftermarket strings are good but I just can't say as I have only tried this set .

I like to change mine once a year. I also shoot 452x material which does not stretch at all. Changing a cam takes some know-how because you have to check for cam lean and adjust the string accordingly.

I change mine about every 2-3 years or 25-30,000 arrows. I do it myself. I have a Bowmaster Portable Press - makes easy work of it.