Im looking for a durable multi to go in crosses with PHT, or the new black babolat poly that comes out soon . I usually like a stiffer feel, but my current string (isospeed professional) went dead after about a week and a half. They are at about 30 lbs. right now, and im looking for something that is durable, maintains tension, without sacrificing too much control. Any advice or suggestions would be very helpful, thanks.