“A motion to intervene in order to appeal the termination of a class action is not governed by the statute of limitations applicable to the original suit. We do not read United Airlines as establishing an inflexible rule that a motion to intervene in a class action to appeal an earlier order in that action is always timely. A district judge has discretion in deciding whether a motion to intervene is timely, and he did not abuse that discretion in this case when he refused to allow belated intervention by a sophisticated litigant with a large stake who had no good excuse for failing to seek intervention (or bringing its own suit) years ago, who violated the spirit albeit not the letter of the statute of limitations, who appears to have acted for strategic reasons, and whose attempt to intervene delayed a settlement, thus further delaying the conclusion of an already protracted litigation.” See Larson v. JP Morgan Chase, 530 F.3d 578 (7th Cir. 2008).