Don't redeem in Y on short haul flights!
Don't redeem in Y for any flight period. Quick example, North American awards, 30000 for N and 45000 for I, which offers better value? When purchasing revenue tickets, J is usually at least 4 times as much as Y.
After a few planning and searches,
I would only recommend redeeming miles for I fares with at least one long/medium haul segment of 3 hours or longer in a WB aircraft with the exception of BKK which awards are scarce and you can buy revenue RT J tickets for under $2000 from Scandinavia.
In addition, many connections through IST require no additional miles. For example, BOS-IST requires 45000 miles, BOS-IST-CDG/LHR/AMS/FRA also requires 45000, if you have the schedule ready and confirmed, always redeem married segment(s), if/when available, to your advantage.