Modern Vespa

I did do a search, but the results are at least 8 years old. So being new these scooters I'm trying to get an idea of how long these bikes hold up without real major problems. I've always had Japanese bikes, so this is a first for me.

2016 Mp3 500ie Sport with 25,230 miles with no issues and I ride my Mp3 hard.
* Regular maintenance performed at dealers and certified shops only. Though I'll be doing the next basic oil change myself.
* Plenty of preventative maintenance done ahead of longer trips
* Never had a mechanical issue that couldn't be easily remedied myself
* No significant mechanical or electrical issues

Some recommended purchases if your going to do your own service

MP3 front fork lubrication bolt. Just buy one and do not leave it permanently installed. Systematically move the bolt from spot to spot to apply grease.
https://www.scooterwest.com/tool-for-lubricating-mp3-fork-bearings-020943y-ia.html

Variator holding tool for CVT
https://www.scooterwest.com/piaggio-500-variator-holding-tool-toolp500v.html

Plan ahead for consumables, especially tires as its an odd scooter size that isn't common. I typically buy new tires about 6 months before I need them. The rest are pretty easy to get such as spark-plugs, brake pads, oil and filters from the major websites in the other posts.

^This pretty much.

If you're coming from Japanese bikes, the best advice I can give is to take the listed intervals with a big grain of salt.

I do a oil and filter service every 3K mi/5K km along with greasing the headstock bearings. These little engines work hard and hold very little oil.

Oil is cheap, engines are not. And DO use the correct specific oil as listed in the owners manual that has MA or MA2 certification.

Brake fluid, tilt lock systems and coolant every 2 years without exception regardless of miles ridden. Ditto on the gear oil, although I tend to renew the diff oil every 6K mi/10K km. Again oil is cheap, hard metal parts are not.

DO follow the book when it comes to belt replacement intervals. Do NOT extend it.

I own a 2010 MP3 500 and I bought it with 16000 miles on it in 6 months I have put 4000 miles to bring it up to 21000 tire is warn out needs varaitor has a lot of vibration all of this I plan to resolve before next season I have most.of the parts just no time to replace them it is my daily driver and I want to drive into Mexico in the next few weeks around Christmas

Got mine in late 2020 with 600 miles on it. Now closing in on 11k miles and ready for the 12k service very soon with everything it entails. I have a trusted mechanic that is very diligent and that knows I value diligence and good work over cost.
What others have stated reflects my own experience after close to 3 years of ownership. With any vehicle, preventive regular maintenance is the foundation for them to stay their best. It is particular important with European bikes, most are built to be babied, not to be ridden every day with minimal attention until they fall apart.
Mine has never had an unexpected issue. It is actually pretty bulletproof if you take decent-ish care of it. Piaggio and Vespa engines are known to basically last for eternity, they are rugged and designed to withstand some serious abuse. I have an ancient Vespa 150 in Europe that still goes strong despite the fact it's been in the hands of my younger sister and her 2 teenage kids...
*If* you want to do your own maintenance (as several experienced posters here do), be warned that pretty much anything requires you to take off the body work, which is a major PITA. I changed the headlight bulb and have sworn off ever doing it again... even taking the windscreen off involves a ridiculous amount of screws and spacers and what not that are eager to fly into several directions...
And if you're over 200lbs, the drive belt is really on its last legs after 6k miles, so make it a priority to not test it much beyond that.

I bought my 2009 about 4 or 5 years ago,
only rode it at motorcycle rallys,
and around our local 1 square mile town.

IIRC, it had about 2300 miles on it then,
today, about 3100 maybe?

it was never, ever, serviced through the entire time...
I got really worried about that, and took it to a Vespa dealer.

asked to do a Full and Complete Service on everything, belts, oil, brakes, fluids, filters....

got kind of expensive, as it needed a Voltage Regulator, that expired the same time a Lightning bolt hit a tree in our yard.

it runs like a top, love the little critter, but it is NOT a long haul m/c to ride.
the downhill slope of the seat is just plain stupid, what were they thinking?

about 3 miles down the road, and my butt is ready to fall off the seat.

I miss the Backrest I had on my Honda Goldwing, my lower back is a basket case, needs support.