My spend has increased in £'s but decreased as a percentage of turnover.
My first year full year (2003-2004) it was 9.16%, it is now down to 6.42% for last year. However, in monetary terms it has more than doubled.
I think that you need to budget each year how much you intend to spend on your marketing and also monitor it's effectiveness.
I realised just last month that an advert I had in a monthly magazine for the past year, costing £47/month, had not returned a single direct response! Dropped!!