No, 5 five years is friggen huge. Those type of contracts should be left for the superstars of the game. Not for an average forward.
Yeah, I would think for someone like RCG, Evans, etc. that you would be okay as a club to lock them in for 3-4 years but 5 would be stretching it. 1-2 would be too short a time to get them to where you needed them if they weren't walk-up perfect fits for your squad and style you wanted to play.
Take Evans for example. He was obviously someone BA saw something in that he wanted in the squad and he was prepared to let the work be done to get him fit for purpose. We are now just seeing that investment in time and effort pay-off but I reckon over the next 2 years we will see the real benefits of having Evans in our squad. Lane on the other hand was an immediate fit and has shown that from the get go.
I reckon RCG is someone we think might need some effort but he has shown in the past (as had Evans) what he is capable of the task for the coaching staff would be to get him back to that level.
Transforming the forwards and how they work as a 'pack' is more complex than just replacing backs I reckon and it takes more time. For years we have been classed as a powder puff pack and come 2020 there is no way Paulo, Evans, Lane, RCG, Brown, Niukore, Stone and whomever else we add could be considered a "soft" pack.