If you do not participate in rated rounds for 6 months you get status “Inactive”. Does it mean you are really inactive compared to others? What is a typical interval for users between their contests?
I ran my script on Oct 31 2021. It collected information about intervals between rounds for all users who have at least one interval, that means who has taken part in at least two rounds. It discovered 283412 appropriated users and counted 4552393 intervals.

95% of intervals are shorter than 113 days.
Percentage of intervals shorter than 183 days is 97,09%.
Mean value is 27,5 days, mediane is 7 days.

Let’s look at the distribution of duration for intervals less or equal to 183.

So it is totally ok to mark users as inactive after a six-month absence. But I was just curious to find out somebody who came back after being inactive for a long time. What do you say about 11 years absence?
. . .
The old rule says that 20% of people drink 80% of beer. It works for users and number of their contests too) If we count percentage of users who were absent for more than 183 days and then came back, it is a little bit more than 20%: 88586 of 381139 rated users = 23,2%.

Were absent
From 0.5 to 1 year — 49376 users
From 1 to 2 years — 25725 users
From 2 to 3 years — 7674 users
From 3 to 4 years — 2850 users
From 4 to 5 years — 1282 users
From 5 to 6 years — 623 users
From 6 to 7 years — 333 users
From 7 to 8 years — 181 users
From 8 to 9 years — 70 users
From 9 to 10 years — 24 users
From 10 to 11 years — 7 users
From 11 years — 2 users

Unbelievable comeback after 4048 days was done by ciprianf and after 4019 days by Fed. These users participated in 3 and 5 contests. Let’s find somebody with more numbers of rated rounds:
Lynncui — 3719 days, 23 rounds
yiuyuho — 3690 days, 24 rounds
rufferzool — 3553 days, 20 rounds
x3mka — 3504 days, 37 rounds

Let’s look at somebody who had more than several contests (just pick up a random number, let’s say 16) both before and after a long absence.
jackiesteed — 3115 days, 48 rounds
RedAnt — 3033 days, 65 rounds

It’s a pity that their history remains hidden, why they left, why they decided to return, I do not know. But if we look at users with current rating more than 3000 it is obvious that even in times they were inactive on CF, they practiced CP.
neal — 1702 days
hos.lyric — 1404 days
KAN — 1165 days

What's about leaders of rating? What is the maximum of their days without contests?
tourist — 167 days
Benq — 85 days
heuristica — 139 days
ecnerwala — 581 days
ksun48 — 225 days
djq_cpp — 308 days
VivaciousAubergine — 618 days
Radewoosh — 53 days
sunset — 223 days
jiangly — 46 days
Um_nik — 60 days
Petr — 175 days

jqdai0815 once came back after 355 days absence. But he left CF with perfect rating of 3681 almost 2 years ago. Is there any chance he will come back?