Insect spray on outside before storing ??

[Zorro55]

In the crevices before winter,

[MoonShadow_1911]

It couldn't hurt, although I never did.

[Pap and Mimi]

Don't use a spray with Deet, it will melt the decals. I had to replace a decal last year after spraying "OFF" to thin out the million bugs that had been attracted by the awning light.

[Riverbug]

We have a terrible time with Asian beetles so finally had our home and sheds sprayed by a local company. Had them do the camper while they were at it. Results have been pretty incredible all around. I just hope we don't grow additional phalanges in a few years.

[sande005]

Most killers are contact poisons, although a few like for ants are meant to be taken back to the colony and eaten. The contact ones generally evaporate fairly quickly, so are only good for the time period they last in the area. And if any gets on a bug while they are still there.
The best killer over time is winter and getting the RV as cold as you can, for as long as you can. Indoor/semi-heated/milder climate storage may defeat that and allow bugs to make it through to spring. But in Michigan - you should have no issues if kept outside, unheated.
Repellants only repel, and again are short lived in an environment. Plus they only work for the specific insects listed - mosquitos, ticks, etc. And have lots of warnings (as do the poisons) about the kinds of surfaces they will damage if applied.
There can be colonies, that find a semi-warm/protected spot to over winter, or can actually keep themselves warm by shear mass and movement. Then you need the pros. But it's a numbers game - if there aren't many, all or almost all will die in the cold. And none reproduce over the winter. Spray if you want, but there is a chance that a week or so later, if there is a milder/sunny day others may move in before the cold really hits. But odds are very high that that will then do them in. Probably the one of the few good things about RV's not being that well insulated!