Not excessively. 

Do we leave that excess in the account after paying the mortgage?

It appears to me that you are being excessively conservative in your time periods per capital expense. 

You can make it clear to the tenants that they will be held responsible for excess damage or waste caused by the animal,  just as if they themselves did it.While you need to be careful to avoid a claim of retailation,   maybe schedule the next couple rent increases to be a couple percent more than you otherwise would,  and bank those funds towards expected greater turnover costs.  

As to "(if) we don't run out of water" I'm betting that one of two things will happen sometime in the future, 1) it will be decided to pipe the Columbia river from Washington the way oil is currently being piped across continents, or 2) a process will be developed to desalinate seawater cheaply or a process will be developed to bring moisture out of the air which can currently be done on a small scale.

There are numerous part time agents in this area doing in excess of $3 million annual volume.I know this comes down to my own goals and risk tolerance, but do any of you have an opinion or advice when deciding who to go with?

The HVAC system was laying on its side underneath the house and moisture, flooding, humid Texas environment really did it in. 

So my buy and hold portfolio does spill off a fair amount of excess cash reserves .

My property manager recommended 4x mowing in the summer (not sure if that's excessive) which comes out to $120/mo

And also what % you guys feel is tipping into excess where it will possibly inhibit other long-term investing goals of buying other properties, etc.