This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
A waiver of a provision fixing the time for performance does not confer upon the adversary party the right to fix the time for performance at his election.1 Under a subsequent agreement to extend the time of performance to a certain date, there is no waiver of the right to treat the contract as discharged by failure to perform at that date.2 If there is no definite extension of time, the adversary party must perform within a reasonable time, and his failure to perform within a reasonable time will operate as a discharge of the contract.3 Waiver of the provision of the contract which fixes the time for performance prevents default as to the time of performance from operating as a discharge; and while the party who has waived such provision may withdraw such waiver, if without consideration, and demand performance within a reasonable time, he can not withdraw such waiver without notice and treat prior defaults as operating as a discharge.4 While a party who has contracted for security for deferred payments, and who has waived such provision, may retract such waiver on reasonable notice and demand such security, he can not do so without giving reasonable notice.5
12 Focht v. Rosenbaum, 176 Pa. St. 14, 34 Atl 1001.
13 Mitchell v. Dougherty, 00 Fed. 639, 33 C. C. A. 205.
14 Warren-Scharf Asphalt Paving Co. v. St. Paul, 60 Minn. 453, 72 N. W. 711.
1 Mays v. Blair, 120 Ark. 69, 179 S. W. 331; Carroll v. Mundy, - la. -, 4 A. L. R. 811, 170 N. W. 700; Drown v. Ingels, 3 Wash. 424, 28 Pac. 759; Opsjon v. Engebo, 73 Wash. 324, 131 Pac. 1146; Cosby v. Honaker, 57 W. Va. 512, 50 S. E. 610.
2 Drown v. Ingels, 3 Wash. 424, 28 Pac. 759.
3 Mays v. Blair, 120 Ark 60, 179 S. W. 331; Carroll v. Mundy, - la. -, 4 A. L. R. 811, 170 N. W. 700; Opsjon v. Engebo, 73 Wash. 324, 131 Pac. 1146; Cosby v. Honaker, 57 W. Va. 512, 50 S. E. 610.
4 Panoutsos v. Raymond Hadley Corporation , 2 K. B. 473 [affirming (1917), 1 K. B. 767]; Prentiss v. Lyons, 105 La. 382, 29 So. 944; Taylor v. Goelet, 208 N. Y. 253, 101 N. E 867; Walker v. McMurchie, 61 Wash. 489, 112 Pac. 500.