1998 Subaru Forester Engine Damage

My '98 Subaru Forester's engine recently dropped the valves to the left side cylinders. We had a local mechanic disconnect the valve stems and the fuel system to that side. The vehicle does function properly (with half the power) but I would like to know an estimate of how long it can last when going about 20 miles a day on mainly rural roads. The only major difference is acceleration,, but the engine is still very strong and I believe it can go another couple months until we get a replacement engine for it. Is that thought accurate?

Need some more info, what do you mean by dropped valves to that cylinder? Your mechanic could have surely disconnected the fuel to the effected cylinders but didn't disconnect the valve stems. Did he unhook the spark plugs? If it is just a cylinder head issue, it would be a fairly simple project. No sense if trashing the engine. I'd be more concerned with the additional load put on the engine.