There are many expressions in English that have double words.  Here is a partial list with examples of how they’re used:

Time:

hours and hours – many hours

        It took him hours and hours to do his taxes.

days and days – many days

        It rained for days and days.

weeks and weeks – many weeks

       He had been working for weeks and weeks on the project.

months and months – many months

       They’ve been trying to sell their house for months and months.

years and years – many years

       She’s been renting that apartment for years and years.

time after time – every single time

       He keeps helping her time after time.

time and time again – periodically

       He returns to Vancouver time and time again.

hour after hour – one hour after another

       He studied hour after hour with no break.

day after day – one day after another

       It kept raining day after day.

day by day – each day

       She has no future plans; she’s just trying to live day by day.

week after week – one week after another

      Week after week she stays at home and doesn’t go out.

month after month – one month after another

      He would ask his parents for money month after month.

year after year – one year after another

      Year after year the rent on their condo went up.

little by little – gradually

      He started to lose his hair little by little.

again and again – repeatedly

       She called his name again and again, but there was no answer.

on and on – continuously without stopping

       He talked on and on about his adventures in Indonesia.

over and over – repeatedly

       She kept saying over and over how lucky she was.

Comparatives:

more and more – a little more each time

      Every day she likes him more and more.    

less and less – a little less each time [uncountable nouns]

      As time went on, he became less and less interested in art.

fewer and fewer – a little fewer each time [countable nouns]

      As time went on she made fewer and fewer typing mistakes.

better and better – a little better each time

      Every day he’s feeling better and better.

worse and worse – a little worse each time

      My stomachache is getting worse and worse.

harder and harder – a little harder each time

      It seems to be getting harder and harder to find a used CDs store.

bigger and bigger – a little bigger each time

      Vancouver is getting bigger and bigger.

longer and longer – a little longer each time

      The waiting time for a trial date is getting longer and longer.

smarter and smarter – a little smarter each time

      His grandson is getting smarter and smarter every year.

stronger and stronger – a little stronger each time

      By working out, you’ll get stronger and stronger.

Other expressions:

round and round – in circles

The children turned round and round until they fell over.

all in all – considering everything

      All in all, it wasn’t a bad movie.

word for word – each word the same, exactly

      She told him what her girlfriend told her word for word.

step by step – all the steps necessary

      There were step by step directions on the back of the package.

item by item – each and every item

      They had to clean everything item by item.

pound for pound – each and every pound

      He can match his brother pound for pound.

street by street – every street

      The police searched street by street for the missing children.

face to face – facing each other

       Their first face to face meeting was at Starbucks.

shoulder to shoulder – touching the shoulder of the one next to you

The union members stood shoulder to shoulder facing the angry mob.