I like to see the same size spring on each side, however some manufactures actually install two different size springs not only in wire size but, also length. Springs are measured in Inches of Pressure Per Turn (IPPT) We use this to convert springs usually to bigger wire size( going down in wire size decreases life cycles ). As long as the Technician got the IPPT's right you should be ok. I don't think the 3 inches in length is going to reduce the life cycles very much. I would bet that the shorter spring is one wire size down from the longer spring. Again I like to see the same size spring however it is not mandatory.

#1 Check to see if the door is balanced. Disconnect the door from the opener and see if it stays on the ground.

#2 Raise the door half way up and it should stay there and not go one way or another.

#3 Raise the door all the way up it should stay in the up position by itself.

If the door is heavy to lift or does not stay in all three of these positions get them back out there.

I would get them back out there for the noise your hearing anyway it should be covered under warranty. The noise your hearing could be the springs are not lubricated and are popping as they unwind or misaligned hinges.

Check out what I told you to and take it from there. Let me know what you find.