What I normally do is convert a stock 21 gear 700c bike into a touring cycle and these generally run for about 500mi without serious issues. After 500mi you can experience busted spokes (carry spares), worn brake pads (carry spares), bad freewheels (bike shop), and other wear-related issues.

I do have problems with hills on these bikes but that's mostly because I tour alone, don't haul a trailer, and insist of having all the comforts of home with me on my rides plus the fun stuff like fishing poles or beach umbrellas.

First I add high pressure touring tires, 85 psi+ or greater and about 1.25" wide. Then I replace the seat with a super-comfort model. After that I crack the wheel bearings open and lube them with Lithium grease. Finally I lube the chain and derailleur wheels so there's very little friction from the chain/drive assembly.

You don't fall in love with these bikes but if you follow river valleys you'll make good time.