How long is kubica racing in F1?

May be...

He's been in F1 since he replaced Jacques Villeneuve at BMW Sauber for the 2006 Hungarian GP. The race was held on August 6th, so as of today (5th March 2008) Kubica has been racing in F1 for 578 days (or one year and almost 7 months to the day, if you prefer).

He finished 7th on debut, but was later disqualified because his car was underweight.

if he does something good in 2008 by giving BMW their 1st win and also to him,makes him be stayed longer in f1.

Kubica started his professional career in 2000, as a test driver for a Formula Renault 2000 car. During his first professional season in Formula Renault, Kubica scored his maiden pole position and also became a member of the RDD. In 2002 Robert won four races and scored a second place in the Italian Formula Renault 2000. He was also seventh in the Formula Renault Euro cup. At the end of the year Robert took part in the Brazilian Formula Renault 2000 held at the Interlagos circuit. This one-off appearance resulted in a dominant win.

this is is 7th year he started being a rookie in 2000, after 1 year the drivers lose there rookie status and become pro drivers.