Count number of columns between first and last data in each row

I have years across the top and a lot of rows (thousands) with data for different IDs. The IDs don't have data for every year and each ID has data for different years.

ID 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
1 53 64 82 79
2 48 61 74
3 42 48
4 34 19 34 55 52 72 93
5 26 40 118



I need to count the differences in years between the first and last data points. So for ID it would be 3 years (2010- 2013). Because each year is in a column I can also use a formula which counts have many columns there are if thats easier.

This would take such a long time to do it manually so I wondered if there is a solution?