ask - calculate capability tunnel VPN IPSEC

[papapuff]

hi there, I' ve been asked to upgrade our firewall device. the challenging is the device must have life cycle at least 5 years, and still capable to support business operational. I' ve been informed about " blue print" of the next of company' s vision. here we go, how I measure if the device that I will buy will still capable to support our business operational? the critical point is about create vpn tunnel. How I measure maximum and ideal VPN tunnel that will be created? hope my question clear enough :D thanks