Note that the 4 month trial is longer than some of the competition, namely Apple Music which is only offering users a 3 month free trial. In fact in some countries Apple has actually started to charge their users a $0.99 fee to take part in the trial, so for some users this trial isn’t even free at all.
However we should point out that Google’s offer is only for new subscribers, meaning that if you’ve never signed up for a Google Play Music account/trial before, then only can you participate. If you’ve taken part in the previous trial then we guess you’d be out of luck. Then again the previous trial was for 3 months and we’re not sure if the extra month really makes a difference in coming to a decision.
There’s no word on how long this offer will last or if it is permanent, however Google’s website states that it is a special offer so perhaps it might not be permanent. More details can be found on the Play Store.