Performance Database - increase statistics retention

Hi,

We have a medium size opmanager setup - 500 devices, 6000 interfaces monitored. We poll most of our metrics each 5 minutes. We have the default retention statistics, so 7 days detailed, 30 days hourly and 1 year daily.
our setup is running in a virtualized environment, with 1 VM windows 2012(opmanager server) 4CPU, 8GB RAM, 1 VM for SQL 2008

My network team would like to increase the polling up to 1 minute for network devices(around 100 devices). They also would like to keep the detailed statistics for longer time, at least 15 days or even 1 month.

I would like to see if the impact won't be too high on the performance of the opmanager server? Size of DB doesn't matter, we have enough storage. But on CPU and RAM, should I expect a large impact by increasing the detailed statistic retention?
I couldn't find any document about sizing, best practice or limitation of statistics we should have. If any please give me the link.

Thx!

Fred