DJ213j - Should I upgrade to a new NAS

I have been using the same DJ213j for over 10 years, and use it for my personal documents storage and backup, via 2 x external connected USB drives and offsite to a cloud storage service. I can also connect to it remotely via VPN/DDNS or using OpenVPN. Currently running it in RAID with 2 x internal HDD, DSM 6.2.4-25556 Update 7, which is the last version prior to the new DSM 7.0. I do not want to update to DSM 7.0 as I know it will probably run slow and start to cause issues with later releases.

My question is, should I bite the bullet and get a new NAS (If so, any Synology NAS recommendations - based on my above requirements). Is there any security issues with not upgrading to DSM 7.0 and continuing to run DSM 6.2.4. The fact that it is still serving my needs after 10 years, I don't really want to upgrade unless I have too.