Revising `check_model()` #1064

Job	Run time
R-CMD-check / macOS-latest (release)	38m 44s
R-CMD-check / windows-latest (devel)	27m 54s
R-CMD-check / windows-latest (release)	29m 31s
R-CMD-check / windows-latest (oldrel)	24m 6s
R-CMD-check / ubuntu-latest (devel)	1h 26m 0s
R-CMD-check / ubuntu-latest (release)	16m 24s
R-CMD-check / ubuntu-latest (oldrel)	16m 53s
R-CMD-check / ubuntu-latest (oldrel-2)	16m 33s
	4h 16m 5s

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