I don't see this as anything different compared to other years back then.
Discount 1997-98 since it was an Olympic year.
1996-97 started on October 4th and the SCF ended on June 7th and that was with a Wings sweep. Had it gone 6 games like the 1999 Final did, that takes us to at least June 11th.
The one thing I can see is all four 2nd round series went at least 6 games (while they were all 4 or 5 game series in 1997), and the 1999 WCF went 7 games, so that may have added 2-3 extra days.