Take care of it and it will take care of you. I bought my '08 at 146K, tore the engine down at 200K, liked what I saw and put it back together pretty much as-is except for AFM delete, new oil pump, timing set, etc. I then proceeded to add a mild performance cam, minor head work to raise compression and a looser torque converter. I now beat on it regularly. I even took the fam on a 1,500-mile trip to Tampa, FL and hauled back a 900lb golf cart on a 400lb trailer and a full cargo hold, confidently and in comfort while averaging 17MPG.
Being a 2013, you have the latest and greatest version of this generation. I don't think they changed anything of any significance for 2014. The AFM system is about the only real concern with these. But, yours should have the most updated variants of the parts and you're keeping clean oil in it, which is the best thing you could possibly do. Keep the transmission happy, too. I highly recommend a Black Bear tune to clean up the factory throttle and shift characteristics to not only greatly improve the drivability, but to prolong the life of the transmission.
As for towing, how big a boat are you talking about? What areas will you be towing in? Does your Yukon have the factory tow package? Post up a pic of your RPO sticker located on the inside of the glove box door.