Are early extensions a good idea?

The Pirates are working on long term extensions for Jose Tabata and Neil Walker.
Is this a good idea in these cases or in general?

I recall John Hart and the Indians doing this in the early 90's and for the most part,the players did not flourish with a few exceptions and the Neal Huntington connection to Cleveland makes sense that he is beginning to consider a similar strategy.

Jose Tabata seems to be going for guaranteed money and the money seems reasonable to lock up Tabata long term,but why the rush?
Pittsburgh has many players in the system similar to Tabata (Alex Presley and Starling Marte spring to mind),players with speed and not a ton of power,at least presently.
The proposed deal would lock Tabata up through his arbitration seasons and take away his first year of free agency.
The contract could also improve Tabata's eventual trade value with his being under contract at a reasonable rate.

Neil Walker is a little older than Tabata,but plays a premium position for his bat,which adds to his value.
However,Walker is not a plus defender and being that the proposed deal for Walker would run into his early 30's,there is at least an average chance that Walker would not be a second baseman at that stage of his career.
Walker's value at another offensive position would decrease significantly and brings questions of whether a long term contract would make sense for him.
Neil Walker also is more valuable to the Pittsburgh Pirates than to any other team with his being a hometown player and his value in the community/fans is higher than it can ever be elsewhere.Can you place a value on such issues?
Yes,if used as a tiebreaker among two or three players for a spot,but it should not come into play for the Pirates.
It may even work for the team,as Walker could give the Pirates breaks that he would not others as far as contracts go.

Would I do these contracts,if I were running the Pirates?
No,but I do not think either are worth screaming about.
I would rather chance a young player breaking out than pay a Lyle Overbay big bucks for sure.
I can see why the Pirates are thinking about these things,but I would not be hasty in making these calls,unless say Andrew McCutchen were interested.
Then,I race to the table and see what type of a deal can be hammered out.....