motorcycles: Would it be too expensive and worrisome to have two motorcycles?

It depends on your finances. I have a Fazer 1000, which I use on good dry days, and a VFR750 for year round riding and the reason is that the Fazer is prone to corrosion from salt gritters in the winter, whereas the plastic fairing on the VFR just needs hosing down and a little alloy cleaner on the exhaust can to prevent rust spots.

The insurance for both bikes is not much more for most people and, since I have a trade policy, it makes better sense to have two bikes for personal use.

My husband has five!

I would save up my money until I could afford a 'flying refrigerator' Honda Goldwing... but I'm not retired yet, do easily have the money, so owning a Goldwing will not appeal to me until a few more years pass by.

Scrap the Dyna.... you already have a 650R Ninja that genuinely preforms without all the baggage of empty bragging and bold face lies.

Uh... maintenance is not just by miles traveled. If you, like, look in any owners manual for a car or any other vehicle it's like, "every 6 months or 5,000 miles" (or whatever) "WHICHEVER COMES FIRST" for stuff like checking / changing fluids (oil, brake). Like really dude. Give me your owners manual and I'll read it for you and tell you what it says. Glad to help.

Lots of people own more than one bike. If you can afford it, go for it.

I do not see how the insurance can possibly be $700 more, but that is your look out. I have two bikes on the road at the moment (and another in need of TLC). Although there are costs associated with it the convenience (and joy) of being able to pick and choose is worth it, to me at least.

Maintenance - some things will be doubled, for example the oil will still need changing a minimum of once a year on both bikes. Anything else maintenance and time related, rather than miles will be generally doubled.

You already know the insurance is more expensive.

Some mileage related things could increase if you ride more - which you might with the choice of 2.

No idea why you would find it "Worrisome"

I have had 2 bikes for years and occasionally 3

Yes it would be expensive. And you will feel trouble with two. Because when u will ride one the frends of u will hire the other. And they will drive it roughly. As they are your friend you cant deny them..