Brewers weren't stupid and realised that hops stored cold deteriorated less quickly.
The preservation of hops is a most important matter to all brewing concerns. The old practice of storing hops in a warm room in a brewery is a most erroneous one, and this has been proved most conclusively by those who have investigated the subject. At the brewery where I am head brewer, we have sufficient storage for 3,000 pockets of hops, probably more, and it is possible to store these hops for three years and then to have them in sufficient condition for use for dry hopping. Hops to be correctly stored, should be placed in a department which is absolutely dry, where daylight is entirely excluded, and where the temperature is kept slightly below freezing point. Some think this temperature too low, and recommend 38° to 40° F.; others consider 30° to 34° F. gives the best results, but from experience we have found that a temperature of from 28° to 32° F. gives the best results. This is proved by the condition of the hops being excellent after three years' storage. Haslam's system of refrigeration is an excellent one for the purpose, as the temperature of the departments is entirely maintained by cold air. A form of freezing or ice machinery employed for the purpose must, of course, vary to suit the requirements of the proprietors of the hop stores, but the reader cannot do better than inspect the different systems before deciding which to adopt. The great advantage in storing hops in a cold store is that when hops are expensive, and the stock on hand should always be sufficient for one or two years’ consumption, the brewer is able to dispense with purchasing any hops during a dear season, and he may then, when he sees a bargain to be obtained, purchase them, especially during a season when prices are reasonable.
Thatcher, Frank, A Treatise of Practical Brewing and Malting (The Country Brewers' Gazette, London, 1907), pages 241 - 242.
Obviously, this optimal storage temperature only became pratical after 1870 and the introduction of artificial refrigeration. Luckily, this was something likely to be available in a brewery. Where cooling of various things - such as wort - was required.
I've seen figures from the interwar period comparing the alpha acid content of hops which had been cold stored with those that hadn't. After a couple of years. the difference was very significant.