For me if there was nothing that is obviously going to cause an issue like tree roots or the line collapsing, I might take a measured approach and start budgeting for having it lined or replaced BUT I would probably wait and schedule it to be done during my next tenant turnover. 

For the time to measure and think.

IF they measure up, you would then, in writing, offer them the opportunity to remain based on your new terms, and your new Rental Agreement (provide a blank copy for review).

Lastly, the length of stay is increased by hitting these two metrics:   75% of all leases fulfill to completion and 73% of those leases sign an extension.We are super dialed in on our metrics and the ways we measure our ability to hit our stated goal and that is complete satisfaction of both our clients - the investor buyer and the tenant.  

For more good measure, I included the lovely Holton Wise marketing blast that went out on the deal.

. - The Bottom Line - My Take on MarketsThe Weekly 3: News and Data to Keep You Informed- Government Releases Experimental “New Tenant Rent Index:” A new measure of rental rates; shows rents are down the last few months.

You’ve made measurable goals.

The guide should help you measure that.

That's getting to a dangerous leverage point by all measure in stocks, a very dangerous point because the stock market has "flash-crash"'s all the time, things move on emotion and there is entire industry built to profit on such moves and they WANT those moves. 

By that measure, we were overdue for an economic retraction when the Pandemic Recession hit.