On all my bikes, spanning 45 years and well over 100k miles, I've never replaced a bottom bracket, spindle or cups. The longest I've gone so far on a single bike is something over 50k, and the hubs and BB were still original when I finally retired it in favor of something more modern.
It's hart to tell you how much BB life you can expect because there are so many styles and qualities. In your shoes, about to start a tour, I'd err on the side of reliability, and replace the BB unless identify the noise and are sure it's OK.
BTW- have a great trip.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.