If they do not respond to your pay or quit in the predetermined timeline, I'd continue, as it's likely this will become a pattern, but you need to talk to a lawyer.

No need to get a lawyer but having a predetermined rate established with a lawyer who specializes in property law could be lifesaving in the future.

Tenants either pay when they get the court notice and realize I'm serious or tell me there is no way they can pay and give me the keys within a short predetermined period. 

I've heard of thermostats that you can restrict to a predetermined range.

While there is some truth to what's being said regarding homes being torn down at what appears to be a rather pre-mature time, especially in comparison to North American homes which may be in use well over 100 years, a lot of the information contained is reflective of theory - derived from a predetermined "depreciation" formula established by the government, in essence, to keep the economy humming.The basic formula was determined by taking the age of all the homes that had been razed, and averaging out their age.

Once I hit a predetermined amount of reserves as others have suggested above, then the excess money goes to other things.  

Early termination is a pre-determined 'fair amount' to cover for damages from early termination.  

What I proposed is that I put in the lease that the upstairs tenant, again me for now, will have use of the laundry facilities for a predetermined period of time.

They use my script, and handle the calls the way I want them to, enter the data where I want, and follow up on a pre determined schedule.

I do have criteria pre-determined and I have that in my ads :) I've been emailing those who are interested my minimum qualifications first, letting them know that I don't want them to lose money on the application fee if they don't qualify.