Very few cars are free of depreciation but I reckon any S1 kept in good order will hold most of it's value pretty much indefinately, specific variations like the 160 more so. You only need to look at S1 Exiges which are worth more than early S2's.
In agreement with Tony on this however bear oned thing in mind: to keep an S1 in top condition and enjoy using it won't be the cheapest option although I haven't done the maths on servicing/replacement parts cost vs depreciation of say, a S2 111S or 111R.
