SLS Maintenance Costs?

[shertex]

Having owned a 1987 300TD for all of four days, I am in the process of learning about SLS systems. Lots of information on this forum, of course. The impetus for my research was my mechanic telling me that my right shock was leaking and finding out (from Sixto, that perennial bearer of bad news) that those shocks are $500 each!

I have no doubt that a properly working SLS is a wonderful thing. But I fear it could be horrendously expensive to maintain. For those of you who've had wagons over significant periods of time, what expenses have you incurred on these 25 year old systems?

I must confess, I am intrigued by the SLS conversion (air shocks), which has been discussed here. For a $179 kit, two hours of labor, and the ability to convert back to the stock system, that's a pretty attractive proposition....especially considering the potential cost of the alternative.