If you run a successful SaaS platform, at some point someone is going to come to you with the question: can I run it myself? If you’re considering offering a private version of your SaaS, this post might be for you. post 
There are a lot of reasons people want private installs. Depending on the nature of your product, some of them are even legitimate.
The companies that want private installs are the kind of companies that can pay well for them. The problem is that the companies that can pay well for private installs are, in general, the hardest companies to do business with.
If you need at least two people to manage the steady state of your stack full time, get ready to hire two more for each private install.
Unless you are willing to bake the cost of every third-party SaaS you use into each private/on-prem install, you will not be able to afford to keep using those products.
If your customer could handle software that has a rolling release schedule and the operational excellence that is required for it, they probably wouldn’t be using your software.
The upgrade issue is real. The capacity issue is real. You need to, for your own protection and the sanity of your employees, bake things INTO the contract. Don’t be scared. The things you’re asking for are not onerous compared to most enterprise contracts.