The 12 days of Christmas have stretched to more like 45, according to research into the nation’s changing festive habits that also suggests outdoor lights are becoming the norm while – for a third of homes – one tree is no longer enough.

Unlike the Christmas carol, which describes 12 days of festivities, a fifth of people – mostly women – begin planning for the holiday at the start of November, according to the John Lewis festive traditions tracker report, which is based on analysis of its sales as well as YouGov polling.

Kathleen Mitchell, its commercial director, said the longer timeframe was explained by customers getting excited for Christmas but also planning ahead to spread the cost.

“While we see a spike in searches for Christmas trees immediately after the summer holidays, people begin shopping in earnest on 10 November – a 45-day run-up to the big event,” she said.

Britons are expected to buy fewer and cheaper items this Christmas as the cost of living crisis forces many to rein in the celebrations. While total spending will rise by 3.4% to almost £110bn in the final three months of 2023, according to retail analysts at GlobalData, higher prices mean household budgets are under huge pressure.

However, after a tough year John Lewis said shoppers were looking forward to the holiday and getting organised even earlier than usual, with sales of its Christmas ranges 10% higher in October than in the same month last year. The number of visitors to its dedicated departments was also up 13%.

Researchers found more thought going into gifts, with homemade presents “one of the biggest trends for 2023”, illustrated by a big increase in demand for candle-, soap- and pottery-making kits.

Established traditions like sending Christmas cards are in decline – the rising cost of postage has resulted in almost a third of people posting fewer of them – but the research found six in 10 plan to buy decorations for the outside of their homes.

The emphasis is on creating a “Chic-mas” scene – think grazing stag not flashing Santa – with the department store chain’s sales of outdoor decorations almost double last year’s level.

Britons are keeping light show costs down with energy-efficient bulbs but the extra cost incurred is deemed “worth it to dazzle neighbours and passersby”.

Decorating the Christmas tree is still the No 1 tradition for many households and many Britons now have two or more to dress. A third of us put up a second “show tree” for the hallway or home office, a figure that rises to almost 40% for households with children.

However, after the huge lifestyle changes ushered in by the pandemic, the nation has been left suffering a fashion crisis at Christmas.

While 43% of people say it is a time for “sparkles, bright colours and bold clothing”, younger Britons do not agree. More than half of the 25-34-year-olds surveyed plan to wear comfy casuals while a third of 18-24-year-olds intended to stay in pyjamas all day.

But after the long buildup, once the presents have been opened and the turkey eaten, even Christmas lovers are eager to dispense with paraphernalia. The tradition of waiting until the Twelfth Night – 6 January – to take down decorations is now ignored by one in three, with almost a fifth taking them down between Christmas and New Year’s Day.