I think it's really up to each individual to decide how much of an issue is. It might not be for you or others, but it is for me.
I've got two C4's each with about 70 ZigBee devices on. Neither run any logic, all of that is in Node-Red so the only App on each is Maker API. There's very little load on either hub, based on the runtime statistics they're idle, something like 0.2% in 25 days.
Both suffer from memory exhaustion after a period of time and need rebooting, usually 3 - 4 weeks or so. After about a week on each, the JVM memory space has deteriorated so much that I can't even save a driver in the editor as I get Metaspace errors (admittedly it's a large driver).
Moving from the C4 to a C5 or C7 would be an easy fix for me, due to those running 32-bit JVM and less prone to memory issues (if at all).
My ZigBee networks are great, perform fantastic, all devices configured and working well. I'd rather not have to build them from scratch (which is essentially what factory resetting and repairing does) because:
- Many devices are in hard to reach places, such as behind wall switches, in the loft, etc
- Many battery devices (such as Sonoff & Nyce) have really short pairing windows. When reset and paired, all configuration needs to be carried out again. If there's a lot of configuration, some devices go back to sleep too soon and miss the configuration, which means it needs to be repeated. Again and again. These took a lot of time and effort to get configured and setup how I want them.
- Depending on the driver, during pairing "configure" is usually called, which mostly sets defaults only. To set actual preferences you usually have to "save preferences" on each device. Again, more time to sort out, especially on devices like Sonoff battery sensors where they don't periodically wake up themselves and need to be manually woken up. Can take many attempts to get the timing right.
So ultimately I choose not to manually migrate to a C7, that's my choice because to me, it's an issue doing so as it's too much hassle. So for now I will just live with it.
But, if the C7 could use the external Nortek for ZigBee then I would order two C7 immediately and move across as it would be a super simple migration, just like it would have been on a C5.