ESXI Host up for 400+ Days,
I have read this question a lot over the years:
“….because ESXi 5.0 is the golden version for us that just works, and the uptime is well over 100+ days, do you think scheduled monthly reboots of hosts are worth it? “

I can ensure you there is no secret to it ,the latest ESXi version is 7.0 according to the supplier.
Now back to those 100+ uptime days :
To be able to reboot or shut down a host, you need these privileges.
- Host.Configuration.Maintenance
- Global.Log event
Always perform the following tasks before you reboot or shut down a host:
- Power off all virtual machines on the host.
- Place the host in maintenance mode.
The best practices recommended by VmWare in terms of ESXI reboot are :
Good question, there does not seem to be a best practice guide on VmwareDocs that can support this topic.

But what happens really if a host is up for a longer than 50 days so to say ( if you have 3000+ hosts of course you will need an army of people only for the Vmotions) ?
Well in the windows world services die, manual interventions create incidents, VM`s can lag without a reason etc. So it is advisable to reboot the ESXI Once in a While.
At a former customer of mine with a fairly big ESX Infrastructure, there were already set maintenance windows and ESXI Hosts were rebooted every 90 days. The delay is subject of discussion, but as always it is better to have them rebooted and healthy, than up and half way dead.
Who has ESXI 5.0 in 2022?
Most people say no one and many say I don`t know. The second statement is quite scary actually.
But migrating from 5.0 to 7.0 seems such an easy next ,next,next task . Is it though ?
The short and painful answer is NO, because you can upgrade to ESXi 5.1, 5.5 or 6.0 and ultimately to 7.0 but think about it mathematically. Four upgrades equal 4 times the potential problems and maybe, just like I saw it in the middle of an upgrade in 2021 one ESXi died and took all the data with him (luckily most could be restore, but it was a huge effort).
So my personal short answer is Keep It Simple, upgrade directly to 7.0 with the prerequisites respected and a well put in place / tested recovery plan.
The upgrade scenarios are quite limitless, Test envirinement first and the rest after.
Divide hosts in two categories an define which one goes first.
Split Windows hosts from linux hosts and so on.
The Vmware infrastructure can be very strong and resilient but pushing it to it`s boundaries is a risk and like many Ransomware Infections have prooven it, it is better to manage risk than manage disaster!