it's nice to see a guy spotting this fallacy.. (that prices always go up)
1. it's true that alot of us would like to see appreciation of price in practically all classes of assets that we invest in.
2. unfortunately, this can't hold water in perpetuity.. (even if the argument is based on inflation, etc.)
3. if you read/remember history way back enough.. you'd realized that inflation is just a flimsy arguments. the lost-decade in japan was attributed by deflation, not inflation.
4. properties are good investment(period).. but is it because their prices always go up? not necessary. it is because they're good hedge for inflation? only up to a point.
the best thing is for you to keep a constant vigil.. because what makes money yesterday may not be a money making asset today (there're economic shifts, political shifts, social/demographic shifts, psychographic shifts, etc constantly at shift)
Ultimately, you need to treat this investment as a business, buy, keep & sell.