Leaving aside the issue of diagnosis, which is worthwhile doing whether you use it to get reasonable adjustments in the workplace, or just to get a better understanding of everyday issues, there are things you ought to consider that are not just a matter of autistic spectrum.
Coming up to 40 is a tricky one in employment, where many jobs expect you to be moving into management by then. People management particularly isn't easy if you are on the spectrum.
However the management circle expects certain social attainments - socially acceptable spouse, membership of the right groups or clubs, perceived ability to conform, including being prepared to turn a blind eye/ignore others indiscretions etc.
Diagnosis may open up easier progression, but it is as well to consider that the world out there is still not good at accepting autistic traits, and with a diagnosis you may still find some areas of opportunity closed to you, just because that's the way the in-crowd behaves.
So also consider that if money isn't necessarily an important issue, could you do more non-management activities and become more useful in non-people magement situations, so you are still valued but not perhaps as promoted as you would like.
In short try not to think of diagnosis as a panacea, and look at other factors.
A diagnosis will help you requesting reasonable adjustments in the workplace, maybe this is what you need to secure a job rather than moving around. There is a stickied thread on the forum about assessment and diagnosis in adults which has plenty of information to help.