Whereas it seems, that this is not directly possible, cause bitcoin script does not allow to reference a transaction "within last 30 days", one could think about a "workaround" with a business logic watching the P2SH address. An approach could be the nested "if", which is allowed in bitcoin script. If ever within last 30 days there was a payment, the 30 days need to get "reset" - maybe you would need to play with two P2SH addresses, and shift the funds to a second addresses (and vice versa). If your business logic discovers a transaction in the last 30 days, the funds are transferred to a second address, and then again to the first address. For this second address you'd have the same set of rules, just the tx output script (for it's address) changes. The business logic could have a "known secret", that noone else knows, and then shift the funds between the addresses, just as an idea, like this:
OP_HASH160 <length 0x14> <SECRET> OP_EQUAL
<business pubkey> CHECKSIG
2 <Alice's pubkey> <Bob's pubkey> <Escrow's pubkey> 3 CHECKMULTISIG
30d CHECKSEQUENCEVERIFY DROP
<Alice's pubkey> CHECKSIG
Obviously it becomes clear, that there are fees involved in such a scenario. It depends on the frequency of transactions within last 30 days, and the value of the funds, that are shifted around. The fees should not eat up your funds... And then again, maybe one might look into using Lightning as "transport mechanism" to shift values around?