I'm not sure what you expect out of an 18 year old van. And it sounds like a hard 138k, carrying 2 and 3 bikes with only a V6.
So, I've been researching this as well. I'm a Chevy man, and I'm on my second Astro. I got my 2000 in '03, and gave my '93 to my son, who totaled it inside 6 months. But when I gave it to him, it had 165k, and ran like a top. My 2000 runs fine, with just over 120k. It's just feeling a bit small for me these days. Both were/are V6, AWD, and sucky mileage. I have broken 20 mpg on a trip once.
So, I'm looking at an Express extended body, less than 3 years old. and the advice given to me said to get a V8 and invest in a programmer to write some economy into it. The theory is that a V8 has some economy to spare, without putting too much strain on it. A V6 is pretty much at it's limit.