Yes, it is a consideration. To a point. It cannot dominate the decision considering the first 10 years of Tanev’s playing years are spent and the remaining 10 years (if he even has that) will likely be at a lower level of play (with a higher $ hit) than he is today. It would be easy to argue that >50% of Tanev’s career value is already spent. Yet to a playoff team, his immediate value (this year and next 1-2 years) is still quite high. Beyond that it drops off sharply.
And considering his current value, we should be able to get one or two B-value assets in return. These assets will have close to a 50/50 chance to succeed/bust similar to a kid like Dahlen or a draft pick like McCann/Boeser.
So you are weighing the value of this player’s longer remaining career, cheaper cost, and better alignment with this team’s competitive window with the risk of busting.
All needs to be considered but in the end I think it clearly ends up in favour of trading rather than retaining. Esp if you factor in that Tanev becomes a UFA in the summer of 2020. If we aren’t a competitive team by then he may leave and then none of these additional years, mentorship, etc will be obtained.