Any tendency to increase block time, for any reason, is probably a mistake. As coins get more popular, they will start making shorter and shorter block times to be more attractive as currencies. Longer block times are penny wise pound foolish in this case.
I do agree with this to an extent. However I think the most transactions that have been in a block for HBN have been like 10... We will likely never even get close to capacity.. 90 seconds is still very quick..