You might want to look past the tires. Check on barely good enough spring packs. Check on frame reinforcement in spring hanger areas. Check on balance from side to side. How much heavy stuff is on one side & what can you do about it?
Yeah, check the tires. Check them everyday. Check for ageing. Check for uneven wear. Check for inflation. Check the numbers & reputation before even buying. Buying cheap might be OK for the weekend warrior headed for the local CG each weekend. Buying cheap is asking for trouble for the long distance traveller.