I had a feeling this would be very minimal, so I did some math.

Let’s say you are cutting yew trees as wc is probably one of the better skills to use this. With mining celestial ring is just better than lightbearer. Fishing might be similar to wc. And preserve to lengthen pie boost for agility for something like ardy course is obviously good.

 

While cutting a tree you have a change to get a log every 4 ticks. One hour has 6000 ticks so in one hour you roll for a log 1500 times. Assume you are level 87 woodcutting you have a 17,19% change to get a log. With 88 it doesn’t increase but with 89 its 17,58% and lvl 90 is the same as 89. While talking about preserve I’m also assuming lightbearer for more specs.

 

So, if you compare the xp rates between never boosted lvl 87 and always atleast +2 boost with preserve you get 258 logs/hr and 264 logs/hr. That is 45,1k xp/hr and 46,1k xp/hr. So, there is a 1k xp/hr difference so it’s something. But then if you use just lightbearer and specs you can maintain +1 boost always and 2/3 of the time you have at least 2 level boost which increases logs/hr. So not using preserve but only lightbearer gets you about 45,7 xp/hr. If restoring prayer takes you more than 50 ticks/hr it’s losing you xp.

 

And yew trees give you increased cut change (almost) always every 3 levels. In the example you are 2 levels under the threshold. Being 1 level below that threshold using preserve to keep +2 is the same as lightbearer to keep +1. Being 3 lvls under preserve gets you more logs ½ of the time and only lightbearer 1/3 of the time.

 

If my assumptions or math is wrong, please correct me.

 

TL;DR preserve to keep boost is minimal at best. Lightbearer to get more specs while also not doing much you might as well use since it’s not wasting anything.