I have 3 different trailers with PTI plates (actually, 2 with PTI plates, 1 with a "one-time" PTI sticker - that was used in the first iteration of the PTI program); I get renewal notices/bills from CA DMV on all 3 trailers every 5 years, and once paid I get a new registration for each. I'm pretty sure that the registrations on mine do in fact show an expiration date.
We don't stop playing because we grow old...We grow old because we stop playing!
2004 Itasca Sunrise M-30W
Carson enclosed ATV Trailer
-'85 ATC250R, '12 Husky TE310, '20 CanAm X3 X rs Turbo RR
Zieman Jetski Trailer
-'96 GTi, '96 Waveblaster II