So this question has probably been answered already, but when using Immortal/Eternal Chronomancer, do Temporal Rift and Enter infinity stack once you've applied them via deadlock? Or is there no reason to stack them past the initial stack?
Once you have 3 stacks of Deadlock, using The Fourth Dimension (5) will activate the "The Fourth Dimension" and as you have this buff applied, whenever you use The Fourth Dimension (5) you will gain 1 stack of Temporal Rift on top of the usual Deadlock stack. It works the same way with Eternal Deadlock (2) while having 3 Deadlock stacks, this will activate "Enter Infinity" which means Eternal Deadlock (2) applies a stack of Infinity Rift on top of Deadlock.
There's a couple things to note about this.
Firstly, when you use either Eternal Deadlock or The Fourth Dimension while at 3 Deadlock stacks, you enter the respective state, but it resets your Deadlock stacks before it applies Deadlock again, meaning you only need to use 3 Deadlock applying skills to trigger the next Enter Infinity or The Fourth Dimension buff. This is good, because it means if you use both skills equally, you are guaranteed to activate both states at some point, assuming you hit every time, which is usually the case, if not, you lose a couple seconds having to adapt to the new stack count to get whichever buff you need.
Secondly, if you miss with ether of the 2 skills while having 3 Deadlock stacks, you still get the buffs which allows you to stack Temporal/Infinity Rifts, but you don't get a Deadlock, nor Rift stack.
It's also good to know what does and does not prevent ability to stack Temporal Rift. Taking Eternity (3) removes both the Enter Infinity and The Fourth Dimension buffs, but you still keep your Temporal Rift and Infinity Rift stacks, but Speed Abrasion (4) removes ONLY Temporal Rift stacks.
The Fourth Dimension, Enter Infinity, Infinity Rift and Temporal Rift all lasts 90 seconds, so once you get up to 4 Infinity Rift stacks, you never really have to worry about that, as long as you trigger Enter Infinity every now and then, since there's no way for the class to remove Infinity Rift stacks via skill uses, so it just becomes a matter of keeping track of Temporal Rift and Deadlock Stacks, then using Taking Eternity and Speed Abrasion at the right times. I prefer to use Taking Eternity just before I use Speed Abrasion, that way I reset the "Infinite Damage" buff and get my HoT on at the same time, not always necessary in a boss fight where you aren't hit that often, but it's just a good habit to have.