solid fuel is certainly not going to last forever.... and when it increases in price, it does not normally come back down like oil does....
my employers sell wood pellets ( about 2 years now ) and solid fuel and we have not received negative feedback yet for wood pellets .
Wood pellets can be purchased in bulk or bags , and MUST be kept dry at all times .
If you are looking at a short term solution ( 15-20 years ) I would suggest solid fuel
If you are in a smokeless area ,( and go for solid fuel ) check out the products you can burn before you decide on a system