constant
inexhaustible
infallible
abiding
assiduous
calculable
certain
changeless
consistent
continuing
dependable
devoted
diligent
dogged
durable
enduring
faithful
faithworthy
fast
firm
fixed
frozen
immobile
immutable
inalterable
indefatigable
indomitable
industrious
insistent
intact
invariable
invincible
inviolate
lasting
loyal
marble-constant
never-tiring
obstinate
patient
patient as Job
permanent
perpetual
perseverant
persevering
persistent
persisting
pertinacious
plodding
plugging
commendable
especial
innate
matchless
never-failing
outward
tolerable
unalterable
unbounded
uncommon
unconquerable
unshakable
untiring
utmost
womanly
ailing
assailing
bailing
baling
curtailing
derailing
detailing
emailing
entailing
failing
flailing
grayling
hailing
impaling
inhaling
jailing
mailing
nailing
prevailing
railing
regaling
sailing
scaling
surveilling
tailing
trailing
unavailing
unveiling
veiling
wailing
whaling