Not strict? They had to release a new LP for Christmas! And remember what they actually did in 1964? Here's a quick re-cap:
January - Christmas shows then Paris
February - Visit to America then begin working on tracks for their new LP
March - filming A Hard Day's Night and In His Own Write published
April - filming A Hard Day's Night and Around The Beatles Show
May - Holidays and NME pollwinners show and show at Prince of Wales theatre
June - more work on songs for the new LP, Ringo collapses and taken to hospital, Tour with Jimmy Nicol on drums: Denmark, Amsterdam, Hong Kong, Australia (Ringo re-joins group), New Zealand then home A Hard Day's Night LP released!
July - Liverpool premiere of AHDN film, filming Thank Your Lucky Stars, recording Top Gear and From Us To You, filming Big Night Out and Night Of A Hundred Stars, mini tour of Sweden
August - mini tour of UK, begin recording their new LP, start 25 date tour of USA
September - continuation of US tour, play Canada, back home and continue work on new LP on 29th.
October - Film Shindig, continue recording new LP, start of 4 week UK tour
November - Gig in Ireland, continue UK tour, TV appearances include: Thank Your Lucky Stars, promo for Top Of The Pops, Ready Steady Go, radio shows include: Top Gear and Saturday Club
December - Ringo's tonsils are removed, Beatles For Sale LP released, record Another Beatles' Christmas Record, commence rehaearsals and then perform Beatles' Christmas Show .
Basically - that's 2 new LPs, one film, a European tour including the UK, an antipodean tour and a US tour all bookended by 2 seasons of Christmas shows!
So yeah, the Christmas deadline for their new LP was VERY flexible - I'm just pleased they managed to produce anything at all that Xmas! ;-)