The person at Jiffy Lube is trying to make Jiffy Lube more money. High mileage oils are by and large marketing hype to get you to pay $.40 quart more (off the shelf price) for basically the same exact oil.
I'm gonna hafta disagree here. I have a 91 Explorer Sport that has had oil changes every 3000 miles. It is now at 155,000. Around 100k, it started having oil leak problems (car has always used 10W30). I wanted to switch to synthetics or a durablend around that time (leak was only a drop or two sliding down the back of the engine. Well, switching to durablend caused oil to drip on the driveway in two spots. I switched back to regular 10W30 and now I have one drop on the driveway.
I saw the high mileage oil by Valvoline and decided to give it a try since I use their regular oil (Explorer) and synthetic (Maxima). Here were the results:
1st oil change: Nothing, still a drip on the driveway
2nd oil change: Engine sounds quieter up too 5000 mile change. It used to be quite noisy just before an oil change. Still have a drip but it is smaller.
3rd oil change: Engine even quieter all the way up to 5000 and the oil drip is now gone. Also, I had a lot of lifter "ticking" as the car warmed up...I don't notice that anymore either.
That is my experience. The heavy cleaning and the "seal swell" additive worked great in my experience. If you're not having any problems (leaking or noisy lifters) I would stick with what you have.