I've had 2 helmets in 13 years.
The first was a 10 year old Airoh that saved my life... I realised this when I took the helmet off and saw that the whole left hand side had been sanded down to nothing but fibre glass.
My current helmet is a Cyber which I bought to replace the Airoh and at the time it cost me around £200 (about $400 at the time). I'm looking to replace it now because the visor is knackered (scratched and hanging off), the inner fabric is all torn and scabby and it has been dropped from my tank... thrown in fits of anger and used as a substitute football on a sunny sunday afternoon.
Should you change your helmet? I dunno after the slide that cost me my Airoh I haven't had any major falls so I cant attest as to its safety. That's a decision you gotta make for yourself but I know what I would do/have done.
1999-2000: Aprilia RS 50, 2000-2000: Suzuki TS 50, 2001-2002: Kawasaki KMX 200, 2002-2006: Yamaha Virago 250, 2007-2009: Yamaha Virago XV 535, 2009-2012: Suzuki GZ 250 Marauder, 2012-present: Kawasaki ZZR 600
"Green is better, I need green!" ~ Max my 2 year old