having two tactics, as mentioned, is a good foil for this problem. However, this post by miguelalves, isnt completely correct. You can use CWBs on either side, with 4 at the back, you are just going to be horrible exposed, ha.
Personally, I use a CWB-A on the left side (luke Shaw) and a FB-S on the right side (bacary sagna).
As to the use of IFs and an AF. Again, miguelalves is not totally correct. The AF is definitely compatible with IFs, however, the support duty of the IFs coupled with the attack duty of your AP will create issues. Just think about it. The support duty causes your IFs to drift inside and play through balls, and/or shoot from deep, not attack the goal like the AF and like miguel suggets.
Personally I play with an IF-S on the left side and a winger-a on the right side, that way my striker remains the main target, but he gets crosses to his head from the right side byline, and through balls to run onto from the left side. I also play with an CAM on a AP-S duty.
If you have an AP-A coming from even deeper, your IFs and your AP will run into one another. The AP-A from the CM position isnt going to spend the whole game in front of the IFs, so he wont be available for the through balls your IFs are instructed to play.
So you have two CWBs on either side driving up the field wide, the two IFs on either side cutting in and playing narrow, and the AP-A also taking up space in the middle of the park, however, none of those three players will be far enough up the field to be available for the CWBs crossing, so thats mostly wasted.
this is a link to a tactical thread of mine that has won me be the PL with a number of teams, including not so great ones.
http://www.fm-base.co.uk/forum/football-manager-2014-tactics/152070-arsenal-possession-tactic-2.html
And to be clear, miguelalves is wrong, only in that he is suggesting there are specific requirements of a tactic. The game is very open, and will allow for success with varying ideas and play-styles. dont limit yourself.
as to the tactic not working in the second year, try tweaking some individual player instructions here and there.