It's one interchange, say around the 60 minute mark and it's not for a " sole purpose", there are more dimensions to it - 1. giving Sims or Friz a rest, 2. Bringin on a big, skillful backrower aginst tiring defence, and 3. Sims or Friz know they can really go at it for the opening 20 minutes of the 2nd half. That's a good use of the bench. I'm happy for some 2nd rowers to play a full 80 but not all are capable and more importantly not all remain effective for that long. Sims I believe is more effective for about 60 mins and while Friz can play 80, why burn him out when we have a capable interchange - ( plus I like Luc on that side ).
Our downfall last year was, I think largely due to player burnout and mostly in the forwards - a big pre-season and a hard ( but fruitful ) first half of 2017 cost us big time. I hear the 2018 pre-season was more measured and sensible. Now we have to manage the troops properly through to Sept with smarter use of the bench and some game time for the young blokes coming through. We're a real chance to make the top 4 this year, I'd hate if we blew it again.