SQL Server 2019

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CREATE TABLE stays(
   ClientID  INTEGER  NOT NULL 
  ,DateStart DATE  NOT NULL
  ,DateEnd   DATE  NOT NULL
);
INSERT INTO stays(ClientID,DateStart,DateEnd) VALUES (1,'2020-01-01','2020-01-31');
INSERT INTO stays(ClientID,DateStart,DateEnd) VALUES (1,'2020-04-04','2020-05-04');
INSERT INTO stays(ClientID,DateStart,DateEnd) VALUES (2,'2020-01-03','2020-02-27');
INSERT INTO stays(ClientID,DateStart,DateEnd) VALUES (3,'2020-01-01','2020-01-07');
INSERT INTO stays(ClientID,DateStart,DateEnd) VALUES (3,'2020-01-10','2020-01-17');
INSERT INTO stays(ClientID,DateStart,DateEnd) VALUES (3,'2020-01-20','2020-01-27');
INSERT INTO stays(ClientID,DateStart,DateEnd) VALUES (3,'2020-02-01','2020-02-07');
INSERT INTO stays(ClientID,DateStart,DateEnd) VALUES (3,'2020-02-10','2020-02-17');
INSERT INTO stays(ClientID,DateStart,DateEnd) VALUES (3,'2020-02-20','2020-02-27');
9 rows affected

create view myview as
with cte as (
	select clientID, min(dateStart) dt, dateadd(day, 90, max(dateEnd)) dateMax
	from stays 
	group by clientID
	union all
	select clientID, dateadd(day, 1, dt), dateMax 
	from cte 
	where dt < dateMax
)
select clientID, min(dt) VIPStart, max(dt) VIPEnd
from (
	select t.*, sum(isNotVip) over(partition by clientID order by dt) grp
	from (
		select 
			c.clientID, 
			c.dt,
			case when count(s.clientID) 
					over(partition by c.clientID order by c.dt rows between 90 preceding and current row) >= 30
				then 0
				else 1
			end isNotVip
		from cte c
		left join stays s 
			on c.clientID = s.clientID and c.dt between s.dateStart and s.dateEnd
	) t
) t
where isNotVip = 0
group by clientID, grp
select * from myview order by clientID, VIPStart  option (maxrecursion 0);


clientID
VIPStart
VIPEnd


1
2020-01-30
2020-04-01

1
2020-05-03
2020-07-04

2
2020-02-01
2020-04-28

3
2020-02-07
2020-04-20


Warning: Null value is eliminated by an aggregate or other SET operation.
clientID	VIPStart	VIPEnd
1	2020-01-30	2020-04-01
1	2020-05-03	2020-07-04
2	2020-02-01	2020-04-28
3	2020-02-07	2020-04-20