Try unifi mobile...

Their bebas prepaid is technically no limitations, no credit expiry, as long as your line is active. All you need to do is perform any outgoing usage, reload your
account, or purchase any add-on passes within 90 days from your last purchase and/or usage date.

Outgoing usage like make a simple call, SMS or using data...

My sis using this package, I would say TM not really make a profit out of my sis due to very minimal usage from her but her line remain active all this while...

The only issue is that Unifi Mobile so far not yet support e-SIM I think...

I actually asked my sis on this...

You can purchase pure data, and no expiry. Let's say you buy 8GB, as long as your acc is active, you can use until whole 8GB data finish only you repurchase new data...

My sis...she topup RM100 to prepare use one year...And probably by end of one year still have balance...

Meaning TM only earned RM100 from my sis in a year...That also if she fully utilized it, in which she hinted she may try to stretch until 2 years if possible...

So ya...truly freedom I guess...

From OP post that truly aim for line longevity, to remain active, just open data for a while / call someone for fun within 10 sec, can last quite some time before need to topup again coz remember starter pack comes with 2Gb of data and some minutes of call.

Even 4G coverage also no issue due to agreement with Maxis recently...

So ya, if you really aim for OP purpose, unifi mobile bebas prepaid is quite a choice.