This year was much like last. There was little midge activity until August and they all seemed to hatch at once. There’s still the random day (Like last weekend) when you’ll meet a couple.
Weather-wise, May and June tend to be the driest and early May might still have some snow on the higher tops.
If you are heading out to the Hebrides then June is best for the machair.
July and August are the peak school holiday months. They’re also traditionally a bit wetter, though August was pretty dry in the Highlands this year.
September and October can both be lovely. At this time of year though, it’s starting to get dark earlier.
As you point out, folk just get on with living/their holidays. I manage to bivvy throughout the year and I’m a complete midge magnet. They can’t fly in any wind stronger than about 5mph and don’t like direct sunlight. Choose your stopping points accordingly and you should be fine.
And buy some Smidge. Not only will it help the midge issue, it’s a very good tick repellent.
Whenever you come, don’t expect to find lots of idyllic, remote spots to camp your van in. The West Coast, Skye etc are overrun with campervans and motorhomes.