Vega is the sensitivity of the option value to changes in implied volatility.
The vega of a long term option is going to be larger than the vega of a short term option as intuitively a long term option is going to be more sensitive to changes in implied vol while a short term option is going to be more sensitive to realized vol (higher gamma for shorter dated options).
Although keep in mind that implied volatility is generally more volatile on the short end of the curve, and a lot of sell side options desks use vega/Sqr(T) to get what is called a root vega, which adjusts for this higher vol of imp. vol.