The lifetime of the shell could be indefinite. The components (pumps, heater, controls, jets etc) will last 5-12 years depending on source water, chemistry and use.
I woud bet that your pump will leak when you start it. 8 years with no use would dry up the pump seal. Pump seal is $8-20 CDN. It may be difficult to replace just the seal, you may break the wet end in the process. Wet end is $70-120 CDN.
Considering the age of the spa, there may be several O-rings or gaskets that will need replacing, mostly in the jet assemblies. These are quite inexpensive.
Hope my vague answer helps a bit.