Need the year to answer correctly.
I have changed timing belt on 97 A3 - 80,000ks - this would be upper distance travelled - be prepared to also replace water pump and idler roller as they are both part of tensioning path - the alternative could be somewhat expensive.
every 40,000 miles
The 2010 Audi A3 has 16 valves.
The 2013 Audi A3 has 16 valves.
The 2012 Audi A3 has 16 valves.
The 2009 Audi A3 has 16 valves.
The 2007 Audi A3 has 16 valves.
The 2008 Audi A3 has 16 valves.
The 2006 Audi A3 has 16 valves.
The 2011 Audi A3 has 16 valves.
The 2011 Audi A3 has an inline 4 engine.