If I had expensive suspension forks and shock I would follow the maintenance interval closely. Keep in mind however that those service intervals are for mountain bikes ridden off road. MTB's are ridden much harder in far more demanding terrain through mud and dirty and wet conditions compared to a standard commuter.
My guess is that the average bicycle rider riding on the street with cheap suspension never services their fork and or shock. MTB riders are more likely to follow service intervals although that's not universally the case.
In my case, I have a hardtail with a rock shox pilot fork that I have never serviced in 15 years of ownership. They work about as well as you'd expect for an entry level fork introduced 15 years ago, which is not very well.
Modern forks and suspension work phenomenally well. It's amazing how responsive they are to both small bumps as well as big hits. Higher quality rock shox and fox forks however, start at around $600 or so.
You have several options:
1.
buy a cheap full sus bike like an M2S, then replace the forks and shock spending at least $1K for the upgrades.
2.
buy a R&M. Unfortunately, you'll be getting a not so high end fork, but instead a suntour aion fork, and x-fusion shock components which I've never heard of before. It has mid tier shimano slx. Decent spec, but it's $3K more than a budget M2S model with a reasonably high quality budget fork and shock upgrade.
https://propelbikes.com/product/riese-muller-homage-gt-touring/
I would go with the budget build if I could find a rack that could support more than the 22 lbs or so standard for seatpost mounted racks. Any ideas there?
3. take a look perhaps at some of the
bikesdirect offerings. I believe they're offering a $2400 full sus e-bike 29er (700c) with a 400 watt hour battery. A solid value on a pre-built bike if you don't mind a bit lower battery capacity.
Swapping out a fork and shock should prove relatively straightforward as long as you're willing to spend.
The thule pack n pedal rack with a 22 kg weight limit is a solution. It gets middling reviews on amazon. 3.5 stars.
https://www.amazon.com/Thule-Pack-P...show_all_btm?ie=UTF8&reviewerType=all_reviews
4.
buy a hardtail mountain bike and add a suspension seatpost. There are definitely some nicer suspension seatposts on the market now, and all are under $200. No problems with a rack or panniers.
You've got plenty of options.