I have 4 rental units which I do very well with and so far can manage, but I don’t know if I keep growing if I’ll be in too deep and over my head to manage risk.

Grow Rich Slow.

Also as you grow as a landlord you could keep appliances and  lighting fixtures that you get on sale and keep them in your garages until needed.

Starting out they are essential and should be used to minimize your risk when your ignorance is highest, but as your knowledge and confidence grows you may out grow contingencies in your offers.See any contingency you put in your offer makes your offer have less value to the seller.

I do intend to continue to grow.

I'm in great shape for my age.

I think one can blame gas, or the age of the baby boomers, or the general economy but whatever you want to blame, RVing is down.

We at biggerpockets are a pretty diverse group as far as background, education, geography, market focus and age, but also potically and socially.

Problem is, I don't think you've got much appreciation of this (you used the words 'play with in a market'...)With this kind of capital at a young age you've literally got the world ahead of you.

We are a middle-aged couple and so far only experienced in buying homes for ourselves to live in.