Sigurdsson will age like fine wine, he doesn't rely on pace or strength like most footballers & has adapted his entire play style to being a slow player that solely relies on technique. He has done this for over 10 years now, and when there are players like Zidane & Laudrup that were playing their best football at 35-36 years old then I just don't see him declining. He might start contributing less frequently in defense but I think he'll still be improving as a player in his 30's.
He will always have his set pieces to fall back on, as well as being able to cut inside on either foot to shoot, cross or pass. I fully acknowledge that Coleman, Gueye & Walcott are only 2-3 years from being liabilities, but Sigurdsson has the potential to play into his 40's.. Although a couple of injuries could always change that.
