There is another downside of focussing on HSBI entirely. If you are for whatever reason (sickness, no time, etc) not posting for a while, your yield from those HSBI will plummet. If you hold HP instead, the yield from inflation plus curation is more or less unaffected (if you have autovotes on).

Hive is decentralized and the beauty is that everyone can build his own stake. By spending so much Hive you give your stake to someone else and trust him/her that the service is indeed lifelong.