S&S ISAs - do platforms tend to remember and exclude those who've had previous cashback/referrals?

FIREmenow

Hi all, A lot of incentivised current account switches more commonly now limit eligibility in some way when a switch reward has been received before.  I was wondering if this tends to also be the case with the investing platforms that offer cashback/bonuses/referral deals?

I have a S&S ISA with ii - I've seen their referal offer, where the referer gets £200 and the referee gets a year's free platform fees.  My husband will soon also be at the point of transferring away from percentage-based fees, so I am debating whether to refer him to ii and whether this would make him ineligible for potentially better cashback deals in the future - either as an existing customer or as a former customer who has transferred away and then comes back.

How long do their memories tend to be in your experience?  Are people slowly cycling around the schemes if this suits their needs and getting deals again?  Recognising that they might start to limit them, even if they haven't so far, so nothing is guaranteed!  Can offers sometimes stack?  For example if there was a cashback deal on for new customers, and they were also referred by an existing customer - I think I read a thread where this did happen for a past ii deal.

Obviously we're not letting the incentives drive the platform choice - he is likely to do a similar thing to me building up his funds on platforms with low/no fees and free regular investing, then when a certain size periodically transfer to iWeb to hold.