I just read this question about long rests being regularly interrupted and this one about how resources are recovered at the end of an interrupted long rest, and another question came to me.
Is the 1-hour limit for an interruption for a long rest the total limit of all interruptions, or is it the limit for each interruption?
I'm a very beginner to the D&D system, so it might be something written somewhere that I haven't found (at least not in RPG Stack, the Basic Rules, and the rules provided in the Starter Set).
I know it might not be usual to have multiple interruptions for a single long rest, but consider the following scenario: A party takes a rest near a goblin hideout. Goblins notice the fire, so they send out scouting groups who get killed – then they send another group to search for the first group after a few hours.
If each encounter lasts for 40 minutes (which is very long, but ignore that for now), does the party have to restart their long rest after the second attack, as the total interruption was for more than one hour? Or can they just resume the rest, as each encounter was less than 1 hour?
If such a long fight seems unrealistic, then consider a different example. Try to imagine a first fight that lasts 10 minutes, and then another interruption. For example, maybe the party is camped under a big cliff, and some rocks fall onto their tents. Thus, they have to fix the damage and remove the rocks to resume their rest (which may take 55 minutes to do, bringing the total time of the interruption to over an hour).
It's not actually the interruption that interests me, or even the possibility that there can be multiple interruptions during the rest – but whether multiple interruptions whose total time is more than 1 hour breaks the rest.
Strictly reading there may be an infinite amount of interruptions per-rest as long as each period of interruption takes less than an hour.
Resting, PHB 186:
A strict reading of (my emphasis):
reads as each of these periods or intervals of interruption to be their own interrupting event for which the rule allows up to short of one hour of interruption. The rules do not state that there can not be multiple interruptions that each amount to short of an hour.
The Rest Variants in the DMG (267) don't provide any further information on interruptions. If you happen to play with Gritty Realism rules the implications of a cumulative state of interruptions would have a severe impact on balancing of those rules.
All resources spend during interruptions of the rest are regained at the end of the rest, see this thread.
Take further note that getting interrupted for more than an hour in a period of time doesn't prevent you from starting a new rest (see above):
A different but less rigorous reading is to take the initial wording of:
and read it as a single downtime period of 8 hours that is composed of up to 2 hours of light activity, up to less than an hour of interruption and at least 6 hours of sleep.
Based on Mark Wells comment: Is it possible to run a marathon of 55 minutes, stop and rest for x time, run for 55, stop for x, etc.?
Yes, under this reading that is possible, but it comes with several caveats.
First, how much time do you have to spend resting during a long rest?
You have to spend at least 8 hours of strict downtime, 6 of which have to be sleep, and you may spend up to 2 hours of light activity. All other activity will interrupt your rest time.
Travel will have the risks that occur while travelling amplified by the risk of losing your rest-progress.
Your DM has a lot of control in this context. I would like to see how you argue that you can fall asleep and wake up at command without depleting resources, depleting resources for the minor benefit of travelling fast under situations of being followed, chased etc. seem like a bearable investment.