Is there any benefit or disadvantage of applying for more than one lot in an IPO ?

It depends on the response to the IPO from investors. If the IPO has not received good response from the investors and it is under subscribed then you may get allotted as many lots you have applied for. This would be a disadvantage to you as it may not open to a positive listing and you may incur losses. In other case, if the IPO is oversubscribed owing to high demand from investors, irrespective of how many lots you applied for, you will be allotted a single lot and that too if selected in the lottery. So, applying for more than one lot is risky with no great benefit coming out of it.