Extend data retention

I'm aware that data retention is determined by amount of storage allocated to LEM. Running the Database Maintenance Report, I see that we're currently sitting at a little over a 6-month retention. We're interested in extended that further out so I'm looking at various options to present to management. I'm aware of the following two options:

1. The easiest option would be to allocate additional storage to LEM by increasing its size.
2. I'm also aware that reducing the amount of events/logs sent to LEM, will, in effect, extend retention as well.

However, I've been reading about separate nDepth and/or database appliances. Would this help us accomplish this?