The 2018/19 data is in the can. Let’s take a look at Celtic’s 8 in a row as far as league points history is concerned.
Points Per Title

The highest points achieved during 8 in a row was 106 in 2016/17, the Invincible season. Lennon’s side racked up 99 in 2013/14, the only other season close to 100.
The lowest of the 8 remains 2012/13 with 79, the only season under 80 points.
But the critical take away from this is the black dotted trend line. There is an almost imperceptible decrease in points over the period.
Celtic have been remarkably consistent and the 2016/17 will prove a tough bench mark to reach.
Manager Averages
If we consider the manager at the time, the average number of points per season is as follows (2018/19 counts as a Rodgers season as he was in charge for 71% of the matches):

There is very little between the three managers. Rodgers is just over a point a season better off than Lennon. And Lennon is just over a point a season better off than Deila.
Being mischievous, I suppose if you are Lawwell, would you pay over two times the salary for 1 extra point?