MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
create table mytable(users varchar(128), files int, fileage int);
insert into mytable values('A',1,42);
insert into mytable values('A',2,17);
insert into mytable values('A',3,4);
insert into mytable values('B',4,85);
insert into mytable values('B',5,73);
insert into mytable values('B',6,11);
insert into mytable values('C',7,6);
insert into mytable values('C',8,9);
insert into mytable values('C',9,3);
SELECT *
FROM mytable t1
WHERE 10 <= ALL
 (
  SELECT fileage
  FROM mytable t2
  WHERE t2.users = t1.users
 )


users
files
fileage


B
4
85

B
5
73

B
6
11


SELECT t1.*
FROM mytable t1 LEFT OUTER JOIN mytable t2
  ON t1.users = t2.users AND t2.fileage <= 10
WHERE t2.fileage IS NULL


users
files
fileage


B
4
85

B
5
73

B
6
11


SELECT *
FROM mytable t1
WHERE NOT EXISTS
 (
  SELECT *
  FROM mytable t2
  WHERE t1.users = t2.users AND t2.fileage <= 10
 )


users
files
fileage


B
4
85

B
5
73

B
6
11