You only need to maintain the investment for renewal of ARI. Once you have PR you’ll no longer need to maintain ARI so you can dispose of the investment if you want.
Permanent residence is permanent and no longer tied to your investment but must be renewed every 5 years. Usual residency criteria for renewal is presence for 6 months out of every 30 and no greater than 24 months consecutive absence however there is a carveout for people who obtained PR following ARI such that ARI residency criteria (7d/year on average and no absences >24m consecutively).