Shashank,

Google and most other search engines only display a max of between 65/70 characters in the SERP. You've got that much space to get your keyword in there and maybe a call to action (although you can further target this in your description where you get a max of 155 charcters before the cut off).

You've also got to ask yourself if you put a 150 character title tag how it will benefit your site, if at all

Also, don't forget that the title/description are used to improve CTR too (and not just for rankings) so having a spammy looking Title with 3 keywords put in the displayed character length with no consideration for human readability will have a negative affect on your CTR.