I am interested to hear what everyone thinks about how you should analyze when the optimal time (financially) is to sell a rental property.  My oversimplified method, which I would love some feedback on/critiques of, is as follows  

Always good to start with assumptions:

1. I assume that any profit I make from a real estate deal will be invested in a low cost total stock market fund.  Since I have a long investing horizon (30+ years) I assume that I will average 7% growth of this investment per year.

2. I assume that the value at which I can sell my property will increase by 1% per year.  I am in a very static housing market, in a town with a small university.  Not much has changed here in the past 30 years and I expect more of the same for the next 30 years.  

3. Since I am not actively shopping for any further real estate investments, I assume that any positive cash flow I have on a property gets immediately invested into the same low cost index fund mentioned above in number 1.  

Analyzing all of the variables this way, it basically comes down to this:  Each year I keep the property, my positives are: (1) cash flow, (2) principal paydown, (3) 1% appreciation in value of property (assumption).  If I sell the property, my only positive to consider is how much interest I can make on my investment of the profit from the sale of the property.  

At a certain point, the 7% interest (assumption) I can make on the investment of the profit of sale of the rental exceeds the amount I make combined in cash flow, principal pay-down, and 1% appreciation.  In this very simplistic model, it seems to me that is the point at which to sell.  Of course of all of this relies on my assumptions being accurate...something that is impossible to project!  

Because I'm sure it will be brought up, tax considerations seem negligible to me considering my tax bracket, my long term capital gain tax being 0%, etc.  

I would welcome some discussion/feedback on this type of analysis.  What other things am I missing and what should I consider?