Servicing of lens.

Dear friends,
I recently found that my SIGMA 150-500 MM, lens has fungus in the second element from the front,though till now there is not any effect on image quality.I want to know how often and how much cost required for servicing of this lens.I am using this lens less than a year and not kept in with any moisture prevent substance like SiO2 JELL or in any air tight container.Can anybody inform me about this matter.
Please help.

No idea what the sigma guys will charge you for this. I guess it will be a couple of thousand rupees. Nevertheless do the cleaning immediately before there is extensive damage, as the fungus will eat up the lens coating and then your lens will be virtually useless.

Thank you very much for your information......