Agreed w/ all the above. Save your Relic Mats
The only characters I would push above R5 ever are those needed for a GL at some point that require R6+, & then maybe a couple others for particularly hard missions or because of the way the character works.
For example..... I have the following.
R6 on 5's for KAM mission. R6 on Malak for shear toughness.
The remaining 3 main characters for my Drevan team are all R5 & my SET is only G12 to this day.
Its all about Mods w/ that team.