Can you count the letter "l" in:
Q: Is it bad practice to put IP addresses into SPF records instead of lookups if you are also in control of the lookedup record? If someone owns a domain that needs to be looked up in an SPF record, is it bad practice for them to put the IP address of that domain instead of the domain itself in order to cut down on lookups? E.g. to stop going over the 10 lookups limit?
I understand that this would result in needing to change two IPs in the DNS records if the IP needed to be changed instead of one change. Is there any other reason it shouldn't be done?

A: As mail server related DNS records are only changed occasionally but queried all the time, it is better optimize the latter. Administrator's Considerations in RFC 7208, 10.1.2 summarizes this well:

There might be administrative considerations: using a over ip4 or
ip6 allows hosts to be renumbered easily at the cost of a DNS query
per receiver.  Using mx over a allows the set of mail hosts to be
changed easily.  Unless such changes are common, it is better to use
the less resource-intensive mechanisms like ip4 and ip6 over a
or a over mx.


A: 
would result in needing to change two IPs

Sounds like an argument in favour of putting the raw address in the SPF record to me.
If the person doing the next migration sees the v4 and v6 address spelled out explicitly in the SPF record, that is just another reminder that at least two records needed to be changed anyway.
In any case, its a good idea to keep a list somewhere easily discoverable that tells the next person doing any changes what else might need an orderly rollover procedure (mta-sts, DANE, ..)

user
There are 49 "l"s.
assistant